How To Clean Your Boat's Freshwater Tank (Plastic & Aluminum)

Cleaning the fresh water tank in your boat is one of the most essential things you should do regularly to ensure smooth sailing. You need safe and clean water onboard to drink, bath, cook and clean. This can only be achieved by maintaining a clean water system. Today, I will guide you step by step on how to clean your freshwater tank, both plastic, and aluminum.

How to clean your boat's freshwater tank:

  • Drain the tank completely
  • Measure 1 teaspoon/gallon of household bleach (aluminum) or vinegar (plastic) into the tank and add fresh water until it’s full
  • Let it sit for 24 hours to sterilize, then drain the water
  • Fill with fresh water and drain repeatedly until all the bleach/vinegar odor is gone

This job should take you anywhere from 5-10 hours.

After this process, your tank should be clean and safe to put in fresh water for use. The problem is that sometimes your tank needs more than this method to be clean. Continue reading to find out how you can leave your tank sparkling clean.

Dirty freshwater tank with black streaks and grass

On this page:

How to ensure the water tank is uncontaminated and squeaky-clean, the freshwater tank refill, filtering and sterilizing the incoming water, related questions.

Sanitizing your fresh water tank will greatly help in removing the strange odor and bad taste of the water onboard. It will greatly reduce the occurrence of coliform bacteria and will ensure the health of everyone onboard.

Fortunately, keeping the water tank in a better condition to provide good-tasting and drinkable water is very easy.

To start with , check if there’s detritus accumulation on the tank. You can do this from the equipped with inspection and cleaning ports on the tank.

To check , put on a sanitary glove and swab inside the tank with your finger. If it’s slimy or emits an odor, your tanks should be cleaned with detergent and sanitized.

If you haven’t cleaned your water tanks properly in a long time, you might find a thick even stubborn crud layer in the bottom.

Even though removing the tank out of the boat and steam-clean it works great, many of the times it’s not practical. For tough cases though, you should probably steam clean them.

Otherwise, you can use the following steps:

  • Empty all the water in the tank
  • Add a few inches of ice cubes in the tank
  • Add a small amount of water for the cubes to slide the bottom of the tank
  • Take the boat in a place with wave action for the cubes to slosh on the bottom of the tank. - The cubes will scrub the bottom as they melt
  • Remove the water filters to avoid the clogging and then flash the tank until everything is clear
  • Make sure you flush with clean water to avoid sanitizing again later

What to Use to Clean Water Tanks?

  • For the first rinse, steam cleaning is the most effective way. If your tank is in bad shape, steam cleaning is the way to go.
  • If you don't have a steam cleaner, use a pressure washer instead.
  • For steel and aluminum tanks , you can use bleach to flush the system.
  • For plastic tanks , you can use vinegar or lemon.
  • You can also get a special Water Tank Flush, which works well, but is more expensive.

This last one works surprisingly well. The organic acids will dissolve any debris. Vinegar, however, won't leave any odors.

Some tips on using bleach

Plastic tanks may retain chlorine flavor, so I'd recommend trying to use vinegar before trying anything else. Also, if you're using bleach, I would disconnect all the outlets. If it gets into your lines, your water will taste like chlorine for a while. It doesn't hurt, but it doesn't taste nice either.

After cleaning the tank from the buildup, it’s time for sanitizing the water system: “System” because it does no good to clean the tank and leave the pump, lines, and others.

You can sanitize the system by adding home bleach 1 teaspoon per gallon or precisely 8 ounces per 10 gallons of the water in the tank.

CAUTION : This bleach is to sanitize the system, it’s not fit for drinking!

Pressurize the water with the system open but turn off the end outlets. Let it sit for 24 hours;

After that flash the water with each outlet starting with the furthest from the pump. Do this with all the outlet and repeat the flush until all the bleach smell is gone.

Warning : for Aluminum tanks, you should not sit the bleach for more than 24 hours. Also, you should not repeat this process for more than twice a year.

At this point, the system is clean and sanitized. It’s now time to fill the water tank with fresh water from different sources; you can get from outside sources or use the onboard water maker to refill the tank (water from the onboard maker is often sterile and pure).

If the water is coming from outside source however you must take extra caution. For starters, make sure the fill cap is in good condition to avoid water leaks into the tank with contaminants. It makes no sense to clean the tank and put in contaminated water from outside.

Ensure the hose pipe that you are using to fill in your tank is FDA rated to use for potable water. Also, before you put it directly into your tank, let the water run first to flush the hose. Understand: a hose with water in the sun can be a home to many living organisms.

Note: A better solution is to have your own horse which you flush after use and store safely.

Also running water will help you to know the condition of the water from the source. If the water looks dirty, don’t fill in your tank with it. It might be contaminated with things like cyst, bacteria or even metals, there is no need to take chances.

Tip: the key to having clean water onboard is usage. Keep the water flowing in and out of the system regularly to reduce the chance of it becoming stale.

IF you are getting water from an outside source that you are unsure of its safety, you must take extra caution to make sure you are getting quality and clean water. You can guarantee this if you use sterilizers and filters.

When buying a water filter, make sure that it has met all the Microbiological Purification Standards. With this, you can eliminate all the cysts, viruses and bacteria from the water.

Alternatively, go for an Ultraviolet Sterilizers. With this, the water is sterilized by UV lamp that produces UV radiation to kill bacteria.

In addition, add a filter to remove other contaminants.

Chemical water treatment

A good alternative to treat the onboard fresh water in the tanks is by use of chemical products. There are different varieties you can find out there although you be cautious to read on the label because different products have different usage. You might find some that just remove the smell and taste of the water while other sterilizes the water to make it bacteria free.

Often, Iodine and Chlorine based products are better solutions to make questionable water safe to use. If this is not available, use home bleach; ½ teaspoon for 5 gallons and let it sit for 30-60 minute and it will be good to drink.

Checking if the water is safe for use

The best way to determine if the water in the tank is safe for use is to have it tested. Visit a local lab. if you don’t know any visit your local health department and they will direct you.

This method though is only valid only for the water in the tank. Alternatively, purchase a self-testing kit, which although they are not as accurate they can indicate if there is a problem with the water.

How to empty holding the tank on the boat? There are two ways that you can empty the holding tank; one, go at least three miles offshore and empty the tank there or go to a fuel dock with a Marine Sanitation Device (MSD) and a waste pump to empty it for you.

How to install a freshwater tank on a boat? The freshwater tank should be installed close to the middle of the boat. Have a small water pump and enough hose. Get the measurement where the hose should run and fit it. Add a T connection to the pickup line on the pump and run one hose into the tank and the other outside of the boat. Next cut the drainage outlet, place the tank to the selected location and fix everything tight and the tank is ready for use.

How to prime a fresh water pump on a boat? To prime water pump on your boat, start by ensuring there is enough water in your tank then checking the filters and screens to make sure they are working alright. Next opening an outlet like the facet to let the air out and it will prime.

Pinterest image for How To Clean Your Boat's Freshwater Tank (Plastic & Aluminum)

John Robbins

One teaspoon in 1/6 of an ounce. One teaspoon per gallon is 1.67 ounces for 10 gallons, not 8 ounces! That is way too much bleach.

Elina Brooks

Thank you for letting us know that steam cleaning is the most effective way to clean a fuel tank, especially if it’s in a bad shape. My dad owns a fishing boat, and he was thinking of getting a new fuel tank for it soon. I’ll be sure to tell him about this before he gets a custom order for his aluminum fuel tank soon. https://www.mycarrenterprise.com/boat-fuel-tank

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How To Clean Sailboat Water Tanks? (An Easy Guide)

how to clean water tanks on sailboat

As a sailboat owner, having access to clean, fresh water is essential.

But how do you ensure that your sailboat water tanks are clean and safe to use? Fortunately, cleaning your sailboat water tanks is a straightforward process.

In this article, we’ll walk you through the basics of how to clean your sailboat water tanks, from why it’s essential to do so to the steps involved in sanitizing the tank.

Let’s get started!

Table of Contents

Short Answer

To clean sailboat water tanks, the first step is to empty the tank and rinse it with fresh water.

Next, mix a solution of 1 cup of bleach and 1 gallon of water and pour it into the tank.

Allow the solution to sit in the tank for 1-2 hours and then rinse the tank thoroughly with fresh water.

Finally, use a brush to scrub the inside of the tank and rinse it again with fresh water before refilling.

Why Cleaning Sailboat Water Tanks is Essential

Cleaning the water tanks of a sailboat is essential for a number of reasons.

Not only does it ensure that the water being stored is safe for use, but it can also help protect the tank itself from damage caused by contaminants, algae, and bacteria.

In addition, regular cleaning and maintenance can help the tanks last longer and remain in good condition.

Without proper cleaning, the tanks can become corroded, contaminated, and clogged, leading to costly repairs.

In short, cleaning the water tanks of a sailboat is essential to ensure that the water stored is safe to use, and to ensure the longevity of the tanks.

Preparing the Sanitizing Solution

how to clean water tanks on sailboat

When it comes to cleaning the water tanks of a sailboat, the most important part of the process is to create a sanitizing solution.

To do this, you need to mix two parts hot water with one part bleach.

This mixture should be stirred until the bleach is completely dissolved in the water.

Once this is done, the solution is ready to be used.

It is best to use hot water for the solution, as the heat helps the bleach to break down any bacteria and other contaminants in the tank.

Additionally, this solution should be made fresh each time you clean the tank, as the bleach in the solution can break down over time and become less effective.

It is also important to use a gentle bleach, as stronger versions can cause damage to the tank.

Once the solution is prepared, its time to move on to the next step of the process.

Filling the Tank with the Solution

When it comes to cleaning the water tanks of a sailboat, filling the tank with the sanitizing solution is one of the most important steps.

To create the sanitizing solution, mix two parts hot water with one part bleach and stir until the mixture is completely dissolved.

Once the solution is ready, fill the tank with the mixture and let it sit for at least 24 hours.

This will give the bleach enough time to effectively sanitize the tank and kill any bacteria or contaminants that could be present.

It is important to make sure that the solution is distributed evenly throughout the tank, as this will ensure that all areas of the tank are properly sanitized.

Additionally, make sure that the solution is not too concentrated, as this could be potentially harmful to the surrounding environment.

Once the solution is in the tank, let it sit for at least 24 hours before proceeding to the next step.

Letting the Solution Sit for 24 Hours

how to clean water tanks on sailboat

When it comes to cleaning sailboat water tanks, allowing the sanitizing solution to sit for at least 24 hours is of the utmost importance in ensuring that the water stored is safe for use.

During this period, the bleach works to break down any harmful bacteria or other contaminants that may be present.

It is important to note that the tank should be kept sealed during this time to ensure that the solution can properly sanitize the tank.

If the tank is not sealed, the solution may evaporate before it can do its job.

During this period, it is a good idea to periodically check the solution and add more if necessary.

Also, it is important to make sure that the temperature of the solution does not drop too much, as this can reduce its effectiveness.

Therefore, it is best to store the tank in a sheltered area with an ambient temperature that is not too far off from the temperature of the solution.

This will help to ensure that the bleach is able to do its job properly.

After the solution has sat for the requisite 24 hours, it is time to empty the tank and rinse it thoroughly with fresh water.

This will help to ensure that any residual bleach is removed, thus making it safe for use.

It is also a good idea to use a brush to scrub the inside walls of the tank before rinsing it, as this will help to remove any remaining dirt or debris.

Doing this will help to ensure that the tank is properly sanitized and safe for use.

Emptying the Tank

Emptying the tank is an important step in the process of cleaning sailboat water tanks.

To do this, start by turning off the power to the tank.

Then, open the valve on the tank and allow all the water to drain out.

It is important to ensure that all the water is completely drained before moving on to the next step.

If any water remains in the tank, it will be difficult to clean it properly.

Once the tank is empty, close the valve and disconnect any hoses or pipes connected to the tank.

This will help prevent any of the sanitizing solution from entering the plumbing of the boat.

Finally, make sure to open the tank access port and allow any remaining air to escape.

Once complete, the tank is now ready to be filled with the sanitizing solution.

Rinsing the Tank

how to clean water tanks on sailboat

Once the tank has been filled with the sanitizing solution and left to sit for at least 24 hours, it is time to rinse it out.

This step is essential to ensure all of the solution has been washed away and the tank is safe to use.

The best way to do this is to use fresh water and a hose or faucet.

Make sure to get all of the corners and crevices of the tank, as this is where bacteria can hide and thrive.

Be sure to rinse the tank until there is no more chlorine smell present, as this is a good indication that the solution has been washed away.

Once the tank has been rinsed, it is ready to be scrubbed and sanitized.

Scrubbing the Inside with a Brush

Once youve filled the tank with the sanitizing solution and allowed it to sit for at least 24 hours, the next step is to empty the tank and rinse it thoroughly with fresh water.

After this is done, youll need to take a brush and scrub the inside of the tank.

This is important as it will help to remove any residue that may have been left behind after the sanitizing solution has done its job.

Its best to use a brush specifically designed for cleaning sailboat water tanks, as this will help to ensure that no damage is done to the inside of the tank.

When scrubbing, make sure to get into all the nooks and crannies of the tank, as this is where bacteria can hide and build up.

Youll want to move the brush in a circular motion to help dislodge any residue that may be stuck to the walls.

Be sure to also scrub the lid of the tank, as this is a place where bacteria can often hide.

Finally, rinse the tank thoroughly with fresh water after scrubbing to remove any remaining residue.

By following these steps, you can ensure that your sailboat water tanks are properly sanitized and safe to use.

Cleaning the tanks periodically will help to prevent any buildup of bacteria and keep your water safe and free from contamination.

Final Thoughts

Cleaning the water tanks of a sailboat is an essential task that must be done periodically to ensure that the water stored is safe to use.

By following the steps outlined above, you can easily and effectively clean your sailboat water tanks.

So the next time you find yourself needing to give your water tanks a good clean, remember the steps outlined here and you’ll be sure to have safe and clean tanks in no time.

James Frami

At the age of 15, he and four other friends from his neighborhood constructed their first boat. He has been sailing for almost 30 years and has a wealth of knowledge that he wants to share with others.

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How to Clean a Boat Water Tank

Last Updated: January 2, 2024 References

This article was co-authored by wikiHow staff writer, Megaera Lorenz, PhD . Megaera Lorenz is an Egyptologist and Writer with over 20 years of experience in public education. In 2017, she graduated with her PhD in Egyptology from The University of Chicago, where she served for several years as a content advisor and program facilitator for the Oriental Institute Museum’s Public Education office. She has also developed and taught Egyptology courses at The University of Chicago and Loyola University Chicago. There are 11 references cited in this article, which can be found at the bottom of the page. This article has been viewed 19,945 times. Learn more...

Having a fresh water system on your boat is super convenient if you tend to go on long boating trips. You can use it to cook, clean, or even take showers while you’re out on the water. Unfortunately, boat water tanks can become home to mold, bacteria, and algae, giving the water an unpleasant smell and taste or even making it unsafe to drink. Keep the water on your boat fresh and clean by cleaning out your tank and disinfecting it with bleach at least once a year.

Emptying out the Tank

Step 1 Turn on your boat’s water pump.

  • The location of the pump and water tank varies from one boat to another. If you’re not sure where to look, consult a schematic of your boat or your owner’s manual, if you have it.

Step 2 Open your taps and let the water run out.

  • Listen for air coming out of the taps. This will tell you that the tank is empty.

Step 3 Shut off the pump to keep it from burning out.

  • Many boats have pumps that automatically turn on after the water pressure drops below a certain level. This is meant to keep your water moving as the level in the tank gets lower. [4] X Research source

Removing Dirt and Residue

Step 1 Open the cap on the tank.

  • In some cases, the cap might be difficult to remove. You may need a special tool to open it. Consult the user manual for your boat or your specific water system. [6] X Research source

Step 2 Use a flashlight to look for dirt in the tank that needs to be cleaned out.

  • If you’re able to get your hand in through the opening of the tank, feel the inside walls. If they feel slick or slimy, that’s a sign of bacterial buildup.

Step 3 Scrub out the tank with a long-handled brush or power washer.

  • If you use a power washer, you’ll need some angle attachments to get into hard-to-reach corners.

Step 4 Turn on the pump and drain the tank.

  • If you emptied the tank completely the first time, it will probably take a few minutes for the water to start flowing again since there will be air in the pipes.

Disinfecting the Tank

Step 1 Turn off your pump and hot water heater.

  • Consult your user manual if you’re not sure where the water heater is located.

Step 2 Remove and clean any filters or faucet aerator screens.

  • To remove your faucet aerators, unscrew them with a wrench. Clean the aerators with hot, soapy water and a scrub brush. If there are a lot of mineral deposits on the screen, you can remove them by soaking the aerator in white vinegar for a few minutes before scrubbing it. [12] X Research source
  • If your pump has a protective mesh strainer, leave that in place. It will help protect your pump during the cleaning process.
  • If your water tank has a vent hose and screen, detach those as well. Clean them with hot, soapy water if they appear dirty.

Step 3 Measure out enough 5% bleach to make a 50 ppm solution in your tank.

  • You can use this chlorine calculator to determine the correct amount of bleach to use: https://www.publichealthontario.ca/en/health-topics/environmental-occupational-health/water-quality/chlorine-dilution-calculator .
  • For example, if you have a 50 US gal (190 L) tank, you’d need to use about 6.7 fluid ounces (200 mL) of bleach.

Warning: Never mix bleach with other household cleaners, since it could create toxic chlorine fumes. Always use bleach in a well-ventilated area.

Step 4 Mix the bleach with 1 gallon (3.8 L) of water.

  • Combining the bleach with water before you pour it in will also help prevent corrosion if your tank is aluminum.

Step 5 Pour the bleach and water mixture into the boat tank.

  • Alternatively, you can fill the tank with fresh water before adding the bleach to the tank.

Step 6 Top off the tank with clean, drinking-quality water.

  • If your tank has a vent, let a little of the water and bleach solution spill out through the vent in order to sanitize the vent line. If the vent is exterior, put a bucket or other container under it to keep the bleach solution from entering the water outside your boat.

Step 7 Switch the pump back on and let the water run until you smell chlorine.

  • It may take a few minutes for the pump to push all the air out of the lines and get the water flowing again.

Step 8 Let the bleach solution sit in the tank for 12 hours.

  • If you don’t have time to let the bleach stay in your water tank for a full 12 hours, try to leave it for at least 4 hours. [18] X Research source

Step 9 Refill and drain your tank 2-3 times or until you can’t smell bleach.

  • If you still smell a hint of bleach after flushing and refilling the tank twice, add 1 teaspoon (4.9 mL) of hydrogen peroxide per 20 gallons (76 L) of tank capacity and flush the tank again. The hydrogen peroxide should neutralize the remaining bleach.

Step 10 Replace the filters and vent screen.

  • Start with the tap farthest from the pump and work your way to the closest one. Make sure to let the air out of each tap to get your system working properly again. [22] X Research source

Expert Q&A

  • Even with regular cleaning, the water on a boat can quickly take on an unpleasant smell and taste. Try adding a little lemon juice to the tank to keep your water fresh longer and improve its odor. [23] X Research source A solution of about 2 tablespoons (30 mL) of lemon juice per .26 gallons (0.98 L) of water can effectively disinfect drinking water. [24] X Research source Thanks Helpful 0 Not Helpful 0

how to clean water tanks on sailboat

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Read a Nautical Chart

  • ↑ https://youtu.be/FM93IVN5fjk?t=9
  • ↑ https://youtu.be/FM93IVN5fjk?t=18
  • ↑ https://www.sailmagazine.com/diy/let-it-flow
  • ↑ https://youtu.be/-Ov-24uJ8oE?t=101
  • ↑ https://youtu.be/-QzsEvw67ec?t=141
  • ↑ https://www.practical-sailor.com/blog/decontaminating-a-tainted-water-tank
  • ↑ https://www.goodhousekeeping.com/home/cleaning/a28198674/how-to-clean-dirty-faucet-aerator/
  • ↑ https://youtu.be/-Ov-24uJ8oE?t=254
  • ↑ https://www.pbo.co.uk/gear/boat-water-tank-treatments-tested-20504
  • ↑ https://www.researchgate.net/publication/15339874_Lemon_juice_as_a_natural_biocide_for_disinfecting_drinking_water

About This Article

Megaera Lorenz, PhD

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How to Clean a Boat Fresh Water Tank...

How to clean a boat fresh water tank.

boating

The water in your boat’s fresh water tank won’t always stay fresh. When it sits in the tank with poor circulation, it eventually takes on an unpleasant odor. That’s why it’s important to regularly clean out the tank the right way, every time. Here’s how to clean a boat’s fresh water tank.

Drain the Tank

how to clean water tanks on sailboat

It’s important to adequately prep for proper drainage. You’ll not only want to have a designated place to drain out the water, but you also should make sure that the place your draining won’t lead to nasty water spilling somewhere you don’t want it. In addition, try to drain your tank somewhere that won’t negatively affect the environment. Then, you can remove the old water to prepare for cleaning. Turn on your water pump, open all of the taps, and let the water drain out.

Clean Out the Tank

how to clean water tanks on sailboat

The key to cleaning a fresh water tank is to allow the new, clean water to do the work. It will be the carrier of the cleaning detergent, the rinsing agent, and will continue flowing through the tank until there’s nothing but a clean tank and more freshwater left.

The question here is, what kind of cleaning agents should you use? Do you use bleach, or should you go with another product?

Be wary of bleach if you’re concerned about the environment. You also shouldn’t use bleach anywhere that could affect the marine life. If you do decide to use bleach, just be sure you have a proper place to drain it after cleaning.

Instead, add the appropriate cleaner—one designed for this specific purpose and with the environment in mind. You can find a plethora of boat cleaning options here at BoatLIFE for the cleaning of your tank!

Mix in your cleaner and fill the tank with enough water to dilute the cleaner to an appropriate amount. You can then turn off the pumps and the taps to allow this cleaner some time to go to work. Leave it overnight for the best results.

Shop Cleaning Products from BoatLIFE

Drain and Rinse

how to clean water tanks on sailboat

Drain the tank somewhere safe, repeating the draining process. Then, rinse with fresh water. Smell the water coming out if you’re still unsure; if it has the odor of bleach or cleaner, rinse again.

Keep in mind that even after a thorough cleaning, your fresh water tank will still not be suitable for drinking—after all, the freshwater you keep in there will tend to stay. However, you can use fresh water for other purposes on the boat, including rinsing its surfaces, especially if you’re sure to keep changing it out periodically.

Keep Your Boat Clean!

Now that you know how to clean a boat’s fresh water tank, are you looking for more great ways to keep your boat in top shape? Investing in boat cleaners will do the trick. BoatLIFE offers the boat accessories, sealants, and restoration products you need to help keep every aspect of your boat in top condition.

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  • Boat Maintenance

Cleaning the Holding Tank

Prevent solids buildup with healthy-head habits..

how to clean water tanks on sailboat

Weve noticed an odor and a buildup of caked-on solids in the holding tank. My thought is to fill the holding tank with fresh water and the right additive, then let that slosh around underway, and then pump it out. What do you suggest for an additive?

Peter Coburn Aria, Alden Challenger Yawl www.northpointyachtcharters.com Rockland, Maine

While there are a few additives that we can recommend to prevent solids buildup and holding-tank odor, none will be particularly helpful as a single-dose solution to dissolve buildup.

Our December 2013 tank-vent filter test found that after 30 months of testing, the only factor that strongly correlated to clumping tank solids was lubricating the head with vegetable oil or mineral oil. In tests, some of the deposits would not come off, even with a directed hose blast. Solid waste is mostly water, and as such, it dissolves in water quickly. Unless you have used oil in the head, your buildup is most likely from toilet paper or calcium carbonate deposits (the result of mixing salt water and uric acid), if you use seawater to flush. If the buildup has completely hardened, theres little hope for removing it, and you can either live with it or shop for a new holding tank. If the buildup is still sludgy, you have a few options.

Perhaps the easiest fix-but one with a higher ick-factor-would be to empty the holding tank, flush it (and sanitation hoses) with fresh water, and then spray the inside of the tank with a high-pressure hose. This works best if your tank has an accessible inspection port like the holding tanks we reviewed in the February 2012 issue ; a hose spray wand may also make this easier. Do not use a drain cleaner in the sanitation system; it can cause more scale buildup and can damage plumbing parts.

Holding tank maker Dometic/Sealand recommends that boat owners empty the tank, then fill it about halfway with fresh water, and add 8 ounces of a liquid, bleach-free, biodegradable laundry detergent to the water before getting underway, preferably for a few hours of sailing in choppy conditions. Sealand Communication Manager Patrick Snyder also suggested adding a large quantity of ice to the tank along with the detergent, to enhance the cleaning action while underway; ice should be added through the access port, if possible.

To avoid future buildup and odors, follow the tank cleaning with healthy-head best practices: add water to the toilet bowl before any solids deposit is made; use only limited amounts of quick-dissolve or single-ply toilet paper (see PS June 2011 online ); regularly add a holding-tank treatment like the PS Recommended Odorlos or PS Best Choice Bactank T3 to the tank; lubricate the head per maker instructions, avoiding oils; be sure the tank is properly vented; flush the tank with fresh water every four to five pumpouts, or more often if you can.

PS prefers the enzyme and biological (bacterial) tank treatments. Odorlos and Bactank T3 were among the top picks in our most recent tests (see PS December 2012) . Marine sanitation guru and author of Getting Rid of Boat Odors, Peggy Hall (via www.sailboatowners.com ) also recommends using Odorlos as a regular holding tank treatment. (The liquid version of Odorlos is the best-selling form, but cruisers may prefer the powder since it requires less storage space.) A bacterial-spore powder, Bactank T3 out-performed Odorlos in our tests.

For more on marine heads and troubleshooting head odor, check out the PS ebook series Marine Sanitation Systems ( www.practical-sailor.com/books ).

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Maintaining Your Marine Water Tank System

  • By Steve D'Antonio
  • Updated: January 9, 2014

Water Filter

Clean water is not an onboard luxury: It’s a necessity. Drinking, bathing, cooking and cleaning all demand a high degree of purity in your potable water system. Begin the analysis of your system with your marine water tank. What is it made from? Has it ever been opened and inspected? Ideal potable water tank materials include 316L stainless steel; fiberglass that is coated with FDA-approved gelcoat; or epoxy and virgin linear polyethylene. Because of its susceptibility to both galvanic and poultice corrosion, aluminum, while used occasionally for water tanks (as well as integrally aboard aluminum vessels), is less than desirable in potable water applications.

Like all onboard tankage, water tanks should be equipped with inspection or cleaning ports. If your tank is so equipped and you’ve never peeked inside, now’s the time to determine if detritus has accumulated. Don a sanitary rubber glove and swab your finger across the inside of the tank. If it feels slimy or emits an odor, the tank’s interior needs to be scrubbed with detergent, rinsed and sanitized.

| |The bottom right hose in this image relies on steel wire reinforcement, which unfortunately is rusting. Seek other alternatives.|

Next, inspect your plumbing. All hoses , tubing and pipes should be rated for potable water use. If they’re not, there’s no telling what sorts of particles or compounds may be sloughing or leaching into your water supply. Hose, plastic tubing and plastic pipe (including fill and vent hoses) should all be emblazoned with at least one of the following designations: NSF61, FDA Approved or Potable Water Approved. Despite its widespread use, clear hose should be avoided due to its propensity to support algal growth. Conversely, opaque polyethylene, copper and PVC plumbing are well suited to potable water applications.

Anyone installing or working on potable water systems must strive to be as careful and hygienic as possible. Tank openings and plumbing ends must remain closed, taped over or otherwise covered unless they are actually being worked on at the time.

Filters can present a first, second and even third line of defense against potable water contamination. When filling tanks, running dockside water through a high-volume inline filter will ensure clean water is brought aboard. (Note: Dockside hoses are notorious for lacking a potable water approval rating.) However, filters containing activated charcoal should not be used for this purpose, as they will neutralize the chlorine contained in municipal water supplies, which will likely allow biological growth within the tank and plumbing. Also, liveaboard sailors who plan on leaving filters on the dock should make sure they have opaque canisters, as clear canisters are ideal breeding grounds for algae.

| |Proprietary potable-water plumbing systems like this one are not only reliable and compact, they are also specifically designed and suited for fresh drinking water.|

Onboard filters that service the entire boat can be installed immediately downstream of the vessel’s water supply pump, and in this case activated charcoal, along with a particulate filter, are an excellent option. These need not be specialized “marine” filters; household units work very well, and replacement elements are both readily available and inexpensive. Alternatively, you can opt to filter only the water that you intend to drink, cook or wash utensils with, using a “point of use” or under-counter unit. These low-volume specialized filters usually incorporate a carbon component and typically rely on a compact filter and dedicated countertop spigot.

Steve D’Antonio offers services for boat owners and buyers through Steve D’Antonio Marine Consulting ( www.stevedmarineconsulting.com ).

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Falling foul: how to unblock the boat's waste holding tank

  • Falling foul: how to unblock the boat's waste holding tank

When returning our boat, the charter company technician informed me that the waste holding tank was blocked on our Sun Odyssey 43 DS yacht and that it would cost me 150 Euros to unclog it. I was a bit annoyed because unblocking a clogged black water tank is a 5-minute job. Of course, it's never a good idea to do this job in the marina or at least not in the daytime. But I told the technician that I would sort it out myself and it was a simple job. So, from my experience, I can tell you exactly how to do it.

How does the boat's waste holding tank get clogged?

Black water tanks clog regularly on older vessels. No toilet paper is allowed down a marine toilet and even though you may tell the crew this several times a day, occasionally someone will throw some paper in. The best way is to answer the call of nature in the sea. Take a leisurely swim far out to sea, fully relax as you do, and then casually relieve yourself. The bidet is all around you, so there's no need for toilet paper. Then swim back to the boat just as relaxed.

YACHTING.COM TIP: Did you know that a clogged toilet is one of the most common reasons for the boat charter company to take your security deposit? Find out what others are in our article — The most common reasons for losing your boat rental deposit . The truth is that taking out deposit insurance  will save your nerves and a lot of money, not just in the case of a clogged holding tank. So, what are the other benefits of getting coverage? Check out our 5 reasons to take out deposit insurance .

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How to unclog a clogged toilet.

But back to the unclogging of the holding tank. So how do we do it? You need to grab a hose, get in the dinghy and paddle to the side of the boat to the pipe through which the tank leads out to sea. Insert the hose into the pipe (it is usually about 30 cm below the surface, so it is possible to do from the dinghy). Inserted the hose as far as it can go and mark how far it goes. Then take it out and wrap the hose with duct tape or electrician's tape so that the hose seals tightly in the pipe. Then just have one person on the dock by the water tap (where the hose is connected), and another in the bathroom by the shut-off valve from the holding tank.

YACHTING.COM TIP: Another thing our clients often ask is how the toilet (known as a 'head') works on a boat. That's why we've put together a guide on this topic — Marine toilet: how to use it . Take a look to find out w hat types of toilets you'll encounter on a boat, how to flush it correctly, what you shouldn't put down the head, how to avoid spilling the contents of the tank and how to deal with a blocked toilet.

And, what to watch out for?

So, I fed the hose into the underwater pipe from the dinghy and pushed the wrapped part tightly into the pipe to seal it perfectly. Then I called out to the dock, "Turn on the water!". I felt the water gurgling in the hose and heard the air bubbling in the waste tank. And then I felt some of the contents of the tank, pushed by the water from the hose like a plunger, shoot out through the vent valve located about a metre above my back, and some of the stinky contents fell in a very graceful arc onto my back, ran down my white T-shirt and onto my clean shorts. In an instant, I was covered in smelly excrement. Disgusted, I yanked the water hose out of the pipe and the fecal matter began to flow rapidly into the clear harbour water. The sea turned brown and I yelled, "Close the tank!". Paul, who was in the bathroom, shut off the valve in a flash and the brown patch stopped expanding. I discreetly sprayed water from the hose onto the patch, dispersing it further away from the boat. In a moment it had all but disappeared. The septic tank was unblocked and I smelt like fecal matter. I climbed on deck and met Jana who, as I passed her, backed away in absolute disgust and asked why I smelled so bad. So, I told her about my new special deodorant and headed to the shower.

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Making life better by water

Keeping your water tank clean

In this article on water tank hygiene from our Boaters Update, we continue our series on boat maintenance with help from the experts at River Canal Rescue.

From the latest gadgets for boaters to the best maintenance tools for boats - it's all at Crick this year

Leisure marine domestic water tanks are typically constructed of three types of material; plastic, stainless steel or mild steel, each with differing maintenance requirements and associated risks.

Types of tank

The highest risk material is mild steel - it reacts with oxygen to produce rust which drastically depreciates the water quality and creates an environment for bacteria to develop. While the bacteria is not known to be dangerous, if a bacterial infection takes hold, it can give the water a foul smell and taste. When inspecting the tank, the bacterial infection will take the form of slime attached to the sides.

Plastic tanks offer greater protection from bacterial infection however, dependent on material and age, they will start to release toxins into the water when they begin to break down so it's important to replace plastic tanks in accordance with their shelf life.

They're also more likely to absorb or hold any chemicals added to purify the water. For example, the chemical in purifying tablets used to flush the system may remain in the water for a year or so and while these toxins are not dangerous, a chemical smell and taste will persist.

The lowest risk material is stainless steel – this offers protection from rusting and bacterial infection and as it doesn't retain toxins, it avoids persistent foul smells and tastes.

Match your maintenance to the type of tank

Stainless steel tanks require a purification cycle of at least once a year. To do this, add a purifying tablet to a full water tank and leave to activate for the advised time period. Once purification has occurred, turn all the taps on and drain the system as much as possible. This will ensure purification flows through the system. Next, refill and flush the tank twice more to evacuate any residual chemical within the system (with the taps on and a running hose pipe in the tank).

Mild steel tanks require the same purification cycle as a stainless-steel tank but they also need deep cleaning every three to five years. This entails removing the inspection cover and power washing the inside. Do not sand down or rub the rust off - rust is not dangerous and the power washer will remove any loose rust and debris build up. Do not paint the inside of the tank (unless specialist paint is used) as this will leach toxins into the water.

Plastic tanks also need a yearly purification cycle, but instead of using chemicals, they should be cleaned out manually using hot water. If the tank is inaccessible a hot water flush will suffice. If a chemical is the only method available, regularly flush the system with fresh water. Furthermore, do not allow water to stand in the tank for long periods of time as this will increase the build-up of toxins in the water.

Finally, filtration is advisable for any domestic water tank. A filter will remove any debris or sediment, drastically improving the water quality and consistency, and there are also filters that can remove toxins. Filtration however, does not replace the need for tank maintenance and if this is neglected, water will be foul smelling/tasting water even if filters are installed.

Thanks again to the experts at River Canal Rescue for sharing their knowledge.

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Last Edited: 11 February 2019

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How To Clean Boat Water Tank? Without Removing It

How To Clean Boat Water Tank

Cleaning your boat’s water tank isn’t more complicated than cleaning anything else. You don’t have to be a professional or have special skills to do it.

The surprising thing is that a lot of boat owners still choose contractors to clean their boat water tank(s), which can cost up to many times the price of a DIY solution. To help you get the task done let’s walk through a simple step-by-step boat water tank cleaning process. knowing that boat water tanks come in different shapes, sizes, and places, some are reachable to remove or accessible inside to clean, and others are hard to get to. But regardless of its reachability or accessibility, and what materials are the tank(s) made of. There is always a convenient way to get the job done.

To make the task easy I will present two methods:  Cleaning the water tank without removing it.  Removing and cleaning the water tank.

Let’s begin with Cleaning the water tank without removing it:

How To Clean Boat Water Tank Without Removing It.

Cleaning the water tank without removing it is not as difficult or complicated a process as some think. Let’s see how:

  • Remove all filter cartridges, aerators at all outlets .
  • Turn off the water heater from the electrical panel. (If installed)
  • Drain the tank completely through every faucet.
  • Fill half of the tank with hot water. A  temperature that does not cause any damage to the tank and water lines (check the manual). approx 50 Celsius – 122 Fahrenheit will be fine.
  • Shake the tank safely as possible. Take the boat for a short trip, about 30 minutes, to churn the hot water inside the system, which helps loosen the stickiness of sticky filth inside. Or try any appropriate way to shake the tank.
  • Drain the tank completely through every faucet. Drain it as fast as you can. Do it while the boat is moving if possible. To prevent any sediments from remaining inside.
  • Fill half the tank with water and an appropriate cleaner. Bleach damages aluminum tanks and has some environmental concerns. Read more about bleach in The Guardian If your choice is bleach Do Not Use More than (approx half an ounce ( 15 Ml ) of household bleach per gallon of water).
Bleach alternatives are a mix of lemon and vinegar ( approx 4OZ – 120Ml ) per gallon. Or my favorite one the regular dish soap will be an effective and inexpensive solution.
  • Fill the entire system with a cleaning solution. Run the water from each faucet until you can see or smell the solution at each outlet.
  • Close and plug all faucets, outlets, and aerators.  Plug all aerators and the tank’s air breathers. Leave the system pressurized with the cleaning solution in it for 4 to 12 hours.
  • Drain the entire system and flush it thoroughly.   Flush it with potable water. Fill and drain at least 2 times, or until you are sure there is no cleaning solution left in the tanks.”
  • Clean and reinstall all aerators, and filter cartridges . Install new ones as appropriate. ( Recommended )
  • Fill the tanks with potable water.  

That’s How you clean a water tank on a boat without removing it.

Now your waters are clean and potable. You may still smell or taste something strange for a while as a result of the cleaning solution or chlorination but it should not be strong or very noticeable, otherwise, you are fine. 

For additional protection, you can install Drinking-Water Filter & Purifier Systems. And keep in mind you have to clean the tanks once a year at least to keep the supply of potable water available.

As for the water tanks that you can remove , cleaning them is not complicated, just follow the following steps:

  • Remove any filter cartridges and any aerators at faucets and outlets.
  • Turn off the water heater (if installed) from the electrical panel.
  • Remove all hoses and fittings connected to the tank. 
  • Remove the water tanks following the instructions manual.
  • Brush, scrape, and wipe the tank from the inside wherever your hand can reach. Use a stick and wrap a rag over the top for places far from your hand.
  • Install the tank in place and connect the lines.
  • Fill the entire system with a cleaning solution (approx. one ounce per gallon).
  • Run the water from each faucet until you can smell bleach at each outlet.
  • Close all the faucets and outlets and plug all aerators and the tank’s air breather, and leave the system pressurized with the solution in it for 2 to 6 hours.
  • Drain the entire system, and flush it thoroughly with potable water (fill and drain at least 2 times) until you are sure there is no residual solution left in the tanks. 
  • Clean and reinstall all the aerators and filter cartridges or install new ones as appropriate.
  • Fill the tanks with potable water. 
  • How to clean a boat’s fuel tank
  • How To Clean Boat Holding Tank
  • How To Clean A Boat Engine Compartment

Boat Water Tank Cleaning Tips & Nots

  • Algae, bacteria, and other contaminants can thrive in the entire water system, not just the tanks.
  • Make sure there is no sediment left at the bottom, a yellowish layer on the inner walls, or any blackish green spots or dots anywhere you can see inside the tank
  • If you removed the water tank(s) and cleaned it with your hands; no need to use more chemicals or keep them in the system longer.
  • Bleach in these concentrations ( Half an ounce – 15 Ml ) and durations will not harm the tanks, plumbing, or pumps. And it will not require a lot of water to clear it out.
  • Bleach causes damage to aluminum tanks and has some environmental concerns.
  • Bleach causes damage to some types of watermakers. Read the instructions in the watermaker manual.
  • The freshwater in your boat water tank will not always be fresh;
  • During the cleaning process, it is noteworthy that repair and maintenance should be carried out if necessary.

Related Questions

How to know if the boat’s water tank is bad?

How to know if the boat's water tank is bad.

The boat water tank is bad if there are doubtless signs such as; odd water smell or taste or color, jammed pumps, clogged filters, visual inspection – sediments and dirt, or through water test . 

How often should a boat water tank be cleaned?

boat fresh water

You should clean the boat’s water tank at least once every two years – annually would be better. Or after a longer storage time than usual. Or if there are signs that a cleaning procedure is needed. 

Final thought

Boat water tank problems can appear in several ways, the water tastes bad, looks dirty, has an unpleasant odor, water testing, or any combination of the four.

The freshwater in your boat water tank will not always be fresh; bad water source, bad filtrations, Leak into the tank, poor water circulation, rust flakes, paint chips, etc. 

Which will eventually lead to contamination of the water with bacteria, algae, or chemicals. 

That’s why it’s important to regularly clean out the tanks the right way, every time.

I hope this guide was helpful. Bookmark this page to remember and come back to it whenever you need it. Share this post to help someone else.

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cleaning aluminum water tank

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I recently purchased 78 sailboat with aluminum water holding tank. Tank is impossible to remove without substantial cutting of fiberglass under salon couch. Any solutions to thoroughly clean this tank? I have removed all existing water lines, etc. but the tank is my big problem.  

What are you trying to clean off the Aluminum Water Tank? Aluminum reacts with air to grow its own oxide coating very fast. This hard, dark gray coating protects the metal. It''s found on all bare aluminum surfaces, including Water Tanks, which, if rubbed, leaves a dark gray mark. If washed off the of the metal, it quickly forms again. It presents no majorhealth hazrd, if left un-disturbed. There are five categories of aluminum cleaners: 1. Mild Soaps and Non-etching Detergents: Non-ionic detergent such as "Joy" a. If a mild soap or detergent is gentle enough o be applied with bare hands, it can be safely used on aluminum without spot testing first. b. Automatic dishwasher detergents should be always spot tested first. Some of these detergents can discolor non-finished and anodized aluminum and can even bleach painted aluminum. c. Non-etching cleaners are acidic or alkaline solutions containing inhibitors that permit the cleaning of the metal without etching. Care should be exercised in their use. 2. Solvent and Emulsion Cleaners: a. These cleaners are relatively mild solutions which can be used for removing dirt and stains that cannot be removed by milder cleaners. b. They generally can be used on bare, anodized, conversion coatings, and porcelain finished aluminum without spot tests, but product directions should always be followed exactly. 3. Abrasive Cleaners: a. These include polishes, cleaners, cleaner polishes, wax cleaners, scouring powders, metal brighteners that contain abrasive particles, and may also include water, oil, wax, silicones, soap, acids or alkali. b. These cleaners depend on vigorous rubbing action along with a chemical reaction, and can remove most dirt, stains, and corrosion products from aluminum and will restore most weathered aluminum surfaces. c. They are rated as moderate and heavy-duty. Abrasive cleaners also include etching cleaners, and special heavy-duty cleaners. d. Household cleaners with coarse abrasives should ONLY be used on aluminum with PORCELAIN FINISHES. Even a very fine abrasive can dull or scratch a highly polished aluminum finish. Fine pumice powder and stainless steel wool (grades 0000 to 00) can be used with these cleaners, but regular steel wool may leave rust stains. 4. Etching Cleaners: Try "AC-266" (Sherwin-Williams), or "Van Glo" (BASF-Wyandotte Corporation) 5. Special Duty Cleaners: Try "Sure Klean Aluminum Cleaner" (ProSoCo, Inc.). a. These cleaners should remove aluminum oxidation, atmospheric dirt and carbon, and other surface stains from all types of aluminum surfaces. b. Domestic soap flakes c. Acrylate emulsion polish From Alconox: http://metal-cleaning.alconox.com/cleaning_aluminum.htm Alconox® Concentrated, anionic detergent for manual and ultrasonic cleaning. Free rinsing to give you reliable results without interfering residues. Ideal for cleaning contaminants from glassware, metals, plastic, ceramic, porcelain, rubber and fiberglass. Excellent replacement for corrosive acids and hazardous solvents. USDA authorized. Dilute 1:100. pH 9.5 Liquinox® Concentrated, anionic liquid detergent for manual and ultrasonic cleaning. Free rinsing to yield reliable results with no interfering residues. Extremely mild and completely soluble in hard and soft water. USDA authorized. Dilute 1:100. pH 8.5 Citranox® Phosphate free, concentrated cleaner and metal brightener for high performance removal of metal oxides, scale, salts and inorganic residues in manual and ultrasonic cleaning. Corrosion inhibited and free rinsing for reliable results and no interfering residues. Ideal for trace metal analysis. USDA authorized. Dilute 2:100. pH 2.5 LUMINOX ® A low foaming, neutral pH detergent for use in manual, ultrasonic, and machine cleaning. This safe-handling detergent can be used for non-corrosive cleaning without chelation or alkalinity waste treatment problems. Recommended for cleaning aluminum and soft metal, alkaline sensitive labware, and medical instruments in aluminum trays. Luminox is free rinsing to eliminate interfering residues. HTH Gord  

I am trying to clean the inside of the tank. Boat has been sitting idle for about a year and there is no telling what has grown inside of the tank.  

I understand that you intend to perform a “prophylactic” cleansing on your Aluminum Water Tank. Subject to the following cautions, a Chlorine Bleach soaking should suffice to disinfect your tanks. The chlorine will kill any mold, and most bacteria - but only a manual scrubbing will remove the scum (and dead mold carcases). Hope you''ve got an access panel... Long-term exposure to Chlorine is not recommended for any metal, Aluminum & Stainless Steel included. Notwithstanding, it should be OK to shock-treat your tanks with Chlorine, provided you rinse very well after. Despite being high in the Reactivity series, aluminum is resistant to corrosion because of the thin layer of aluminum oxide (Al2O3) which forms on its surface in air. The oxide layer protects the metal beneath and renders it inert to any further reaction. The thin oxide layer will react with an acid or alkali to form the corresponding aluminum salt + water. The exposed aluminum metal will then further react with acid or alkali to form the aluminum salt + hydrogen. For this reason, aluminum cookware, water tanks (etc.) should not be allowed to come into prolonged contact with citrus fruits or vinegar (acids), or alkali cleaners such as caustic soda (sodium hydroxide). As with the other elements, aluminum is absorbed and accumulated in the body, and has been linked to serious illnesses including osteoporosis, extreme nervousness, anemia, headache, decreased liver and kidney function, forgetfulness, speech disturbances and memory loss (Alzheimer’s). Aluminum and chlorine do not react rapidly at room temperature, but if the aluminum is heated, the reaction is vigorous. The product is aluminum chloride, a white powder that fumes in air, reacting with water to form HCl gas and aluminum oxide. Chlorine gas is poisonous and a very strong irritant. Inhalation of chlorine should be avoided. The reaction is sufficiently exothermic that some chlorine and aluminum chloride dust may be formed in the tank, so proper ventilation is necessary. Anhydrous aluminum chloride reacts violently and exothermically with water, forming hydrogen chloride, which is an irritant. Inhalation of aluminum chloride dust can irritate or burn mucous membranes. HTH Gord  

Bermuda

Personally I would never use any cholorine product of any kind in an aluminum tank. Again, this is just IMHO, but you are much better off and doing your tank a much better service if you use and industrial strength food grade Hydrogen Peroxide. I believe the concentration I have used in the past has been around 35% but if you take my advice then I recommend that you be very careful with it because although at that strength wont have the effect on your tank that chlorine will it can have serious effect on your skin. Capt Bruce boatskipper.com  

RichH

If you have access to a ''technical water'' company .... one who specializes in Reverse Osmosis or Ultrafiltration Membranes ---- "US Filter", Minntech, or similar local firms, see if they wont sell you some "Peracetic Acid". Peracetic Acid diluted to a 1% concentration will kill just about everything inside your tankage within a few hours --- but wont dissolve all the debris so you''ll have to periodically add some ''disinfectant'' to retard new critters from eating all the ''old dead bodies'' that remain. Peracetic wont be aggressive vs. aluminum as would Chlorinated mixes. 1/2 gal. of peracetic diluted per 50 gallons of tank water should do the trick .... and with minimal ''damage'' to the aluminum but any acid will dissolve ''some'' of the aluminum. The solution can be dumped directlly overboard when done soaking .... or simply dump a few boxes of bicarbonate of soda into the bilge, etc. and mix there to neutralize before discharging. Obviously you will have to thoroughly and repeatedly rinse the tank until all is totally diluted out. Obviously the usual ''chemical safety warnings'' apply: heavy rubber gloves, chemical goggles, vinyl apron, knowledge, etc.  

35% hydrogen peroxide is extremely dangerous for a non-chemist to use. Buy your peroxide from a drugstore (~5%) ... much safer and wont make things go BOOM. ;-)  

cleaning aluminum tank additional question My 1993 boat has aluminum water tanks. There is so much aluminum oxide debris in the water that it clogs a screen before it gets to a water filter I would like to use. One owner says he just flushes the tank burning out one water pump per season. The tank has multiple baffles making only a small area accessible to scrub through an access port. I'm hoping there is a better way than burning out my pump! I guess I will be doing a lot of siphoning before I launch this year!  

something else isn't right. I have 30 year old alum. water tank. I check the screen in the pre-filter and it needs cleaning about once a month.  

sailingdog

Sorcerer— How heavily chlorinated is the water in your area? Chlorine can cause an aluminum tank to deteriorate like that... and it sounds like you're in an area that uses fairly heavy chlorination as part of the water treatment.  

Chlorinated water in aluminum tank SailingDog: The area I'm in has a previous owner who told me he had flushed the tanks of my boat and left bleach in the tanks to shock them. He succeeded in shocking me too. I'm afraid this was his way of freshening up his tanks - a method that I will not be using in the future.  

sorcerer33 said: SailingDog: The area I'm in has a previous owner who told me he had flushed the tanks of my boat and left bleach in the tanks to shock them. He succeeded in shocking me too. I'm afraid this was his way of freshening up his tanks - a method that I will not be using in the future. Click to expand...

You mentioned thorough cleaning because you couldn't get the tank out to replace it. Just a thought, but if you can access the top of the tank, you could cut an access opening and use the tank to support and protect a bladder. Sealing it with epoxy is another option, but I don't have enough personal experience with that to comment on it. West System has some water tank info on their site and their info on other epoxy applications is pretty good.  

aluminum tanks I just had my aluminum hull cutter in the yard for bottom paint and zincs and was told by the yard manager they had an aluminum hull NOAA vessel in for hull repairs that had integral aluminum freshwater tanks. I was told that when calcium deposits cut off the oxygen to the metal it begins to corrode as happened to this vessel resulting in major repairs to the hull. I pulled the inspection plate on my integral freshwater tank after hearing this and discovered (to my horror) what looked like seaweed in the tank. apparently when this boat was built or re-fit, a coating was sprayed inside the tank to possibly prevent calcium deposit build up??. I have owned the boat several years (A custom build, I am the 4th owner) and have been occasionally adding a cup or so of household bleach to the water to kill any bacteria. (big mistake!) Apparently the bleach dissolved most of the coating leaving quite a mess in the tank as well as some minor pitting of the tank walls. So I have a similar (or worse) situation. My tank also cannot be removed. To clean it will be difficult due to baffels and the only access is the inspection plate (about 18" X 24"). Going in through the outside hull is also near impossible due to an encapsulated concrete filled ballast keel. (the tank is 40Gal centerlined amidships) The only way I see to access it is by removing the cabin sole above the tank (nicely done teak & cherry) Then I think the best option is sand or soda blast to clean and remove the pitting. From what I have learned as long as oxygen is present and calcium not allowed to build up the tank will last. I also admit to not being an expert in electrollisis (I cant even spell it!) and corrosion in aluminum before buying a boat with aluminum tankage. Any advise or suggestions would be appreciated.  

CapitanDon said: I just had my aluminum hull cutter in the yard for bottom paint and zincs and was told by the yard manager they had an aluminum hull NOAA vessel in for hull repairs that had integral aluminum freshwater tanks. I was told that when calcium deposits cut off the oxygen to the metal it begins to corrode as happened to this vessel resulting in major repairs to the hull. I pulled the inspection plate on my integral freshwater tank after hearing this and discovered (to my horror) what looked like seaweed in the tank. apparently when this boat was built or re-fit, a coating was sprayed inside the tank to possibly prevent calcium deposit build up??. I have owned the boat several years (A custom build, I am the 4th owner) and have been occasionally adding a cup or so of household bleach to the water to kill any bacteria. (big mistake!) Apparently the bleach dissolved most of the coating leaving quite a mess in the tank as well as some minor pitting of the tank walls. So I have a similar (or worse) situation. My tank also cannot be removed. To clean it will be difficult due to baffels and the only access is the inspection plate (about 18" X 24"). Going in through the outside hull is also near impossible due to an encapsulated concrete filled ballast keel. (the tank is 40Gal centerlined amidships) The only way I see to access it is by removing the cabin sole above the tank (nicely done teak & cherry) Then I think the best option is sand or soda blast to clean and remove the pitting. From what I have learned as long as oxygen is present and calcium not allowed to build up the tank will last. I also admit to not being an expert in electrollisis (I cant even spell it!) and corrosion in aluminum before buying a boat with aluminum tankage. Any advise or suggestions would be appreciated. Click to expand...

Snboard976

I wonder if I'm looking at aluminum oxide or calcium deposits in my aluminum tank? Removing the tank is not an option - teak & holly floor would have to be removed as well as sink cabinetry etc. Baffles in the tank make installation of a liner or bladder near impossible. I was told by someone with a knowledge of chemistry to use the product that is placed in a shower and sprays automatically to kill mold. He also said hot water was the best wash to use.  

What do the deposits look like? Aluminum oxide is usually a greyish color... but tends not to form except as a layer coating the metal. If the deposits are collecting, it is likely aluminum chloride instead, which is often a whitish powder. Many of the products that are used to kill mold/mildew are not safe for use in potable water systems.  

Now, This is becoming very important to get installed a rain water tank in a house to save the water and making the country save and secure in future. water tank  

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Main navigation, how to clean a marine holding tank.

March 5, 2023 by Alek Eccles

how to clean water tanks on sailboat

Bottom line, if you are a boat owner with an on-deck toilet that gets used, proper upkeep of the marine holding tank is an important and necessary job. Whenever maintenance is regularly performed, it will make less work of this least pleasant of tasks, because as with many things, the longer you leave something, the worse it tends to get. And any holding tank problem that results in repairs is undesirable as it is often expensive and can leave you and your boat docked up on shore rather than out on the water.

In this guide to marine holding tanks and how to clean them, we will cover the good, general maintenance that is needed to keep your system clean and operating optimally. In addition, we will outline the basics, some common considerations, problems and troubleshooting that are frequent to help care for your boat’s septic tank. 

First, let’s review the basics on marine holding tank systems.

Marine Holding Tanks 101: The Basics

The marine holding tank is also known as a blackwater tank and marine sanitation device. A blackwater tank is a container designed and designated to hold human wastes ( and this only ) that are flushed down a toilet. On boats, this is often referred to as a head. 

how to clean water tanks on sailboat

There are laws* that cover the proper handling and disposal of wastes aboard marine vessels. If the boat is equipped with a head, law codes often require a Type III Marine Sanitation Device ( MSD: a.k.a. your holding tank ), to be installed as it is unlawful to directly discharge wastes unless in specific zones*. 

While more complex devices are available, most boats are fitted with a simple holding tank system that features only a few parts. The MSD will often include: (1) the wastewater tank, (2) head inlet, (3) air pressure vent hose, (4) pump out discharge outlet, and (5) often: a macerator and thru-hull, overboard seacock. 

To define these parts of the marine septic tank system:

  • Wastewater Tank: Holds liquid and solid wastes until time of proper removal. Commonly manufactured from polyethylene plastic with volumes frequent from as small as 3 gallons up to 280 gallons.
  • Head Inlet : Connects the flush toilet to the holding tank for receipt of wastes.
  • Air Pressure Vent Hose: Exterior port that prevents over-pressurization of the MSD and allows air flow for pumping of tank contents.
  • Pump Discharge Outlet: All-important holding tank outlet and to-deck connection pipe for pump-outs when docked.
  • Macerator and Seacock: Comparable to a sink garbage disposal, macerators chop and liquify wastes and allow overboard release via the seacock when in an approved discharge zone.

how to clean water tanks on sailboat

Marine Holding Tank Maintenance: Pumping & Cleaning

If a boat’s living quarters or restroom has an unpleasant or lingering smell, this can indicate it’s time to pump and/or clean your holding tank. It can also mean that maintenance needs done more often or that something is lacking from the regular routine. If you live for periods of time on your boat or are a weekender during the season, then your black water tank system is regularly used and caring for it is vital if you want to have an odorless cabin and a functional system.

If properly maintained, a marine holding tank should not experience hard tank deposits, calcium carbonate, or “concrete” type sludge. Waste and sludge should never be left so long in the holding tank they solidify as this becomes a different problem and will require a different, more work and cost intensive solution.

Steps to Tank Maintenance

Tank maintenance can be broken down into four parts: (1) Pumping, (2) Flushing, (3) Treatments, ( optional but helpful ), and (4) Troubleshooting ( when something’s not gone to plan ).

  • Pumping: Marine holding tanks have plumbing that connects to the deck plate where they feature a pump-out valve. Pumping a black water tank is a matter of knowing when it’s time to pump and following the directions at the pump-out service station at port.

how to clean water tanks on sailboat

  • Pump the holding tank when the tank gauge ( or a fair estimate ) indicates it’s no more than 2/3 full or when a bothersome odor is hanging about the boat.
  • Pump out directions tend to be fairly straightforward and are often posted at the equipment. In general, pumping includes: (a) opening the boat’s on-deck discharge port, (b) connecting the service pump plumbing to the boat fitting, (c) opening of any valves if present, (d) turning on the pump, (e) pumping until sight glass pumps clear, (f) cleaning, returning and/or shutting off the service pump, and (g) ensuring your boat’s deck fitting is capped and valves are closed.
  • Flushing: Wastes that enter the holding tank are water soluble or will suspend in water, which means they can be removed by flushing the tank. To flush, first pump the tank dry, then fill with freshwater and re-pump. 

Flushing promotes further break up and removal of any solid wastes left behind after the initial pump out. This process may need performed multiple times. Repeated flushing of your MSD system is often all that is needed to dislodge and clean out a layer of accumulated tank sludge. 

  • Treatments: Common marine holding tank treatments include enzyme and/or nitrate additives. While not necessary for a healthy, operational tank, additives promote tank cleanliness, reduce odors and can make regular cleaning easier by helping to break down wastes and sludge.
  • Troubleshooting: Sometimes MSD maintenance does not go as expected. When problems arise: do a step-by-step troubleshoot. Some common problems with marine holding tanks:

(1) Loss or insufficient amount of suction can be due to a pump priming problem or a bad pump diaphragm. In these instances, ask for help or service from the pump station owner.

(2) Tank contents are not being removed by the pump can be due to a clogged outlet plumbing on the holding tank, or an unopened or clogged tank vent line, which can result from debris, insect activity, toilet tissue or wastes within the vent plumbing. Both cases can often be fixed using a plumber’s snake.

(3) Sludge layer remains after flushing the holding tank can be a result of too much time between maintenance. Sometimes filling the holding tank with clean water and agitating the water by chopping the boat can break up materials for their removal. If this doesn’t work, add a small amount of liquid detergent and repeat the agitation and flushing process.

how to clean water tanks on sailboat

Important Maintenance Notes / Considerations

  • Drain cleaners are a definite no for a marine holding tank. Using them can actually increase the buildup of scale within the tank ( due to chemical reactions ) or it can attack plumbing components and parts ( due to the chemicals in the cleaner ), causing damage that can lead to costly failure and replacement of the system.
  • Preferably use freshwater rather than seawater to flush onboard toilets as well as to prime the holding tank. The use of seawater can react with chemicals associated with human wastes and its breakdown ( uric acid ) that will lead to scale deposits ( calcium carbonate ), which can be fairly difficult to remove.

Final Care Considerations for Marine Holding Tanks

  • Always: use bathroom toilet paper listed for marine vessels, RVs, or septic tanks only. These types are designed to break down and apart quicker, making it less likely to experience a clog or other issues.
  • Never: flush anything other than wastes down the head: biodegradable or not. The entire MSD system and pump-out stations are intended to handle human wastes only. Food, personal care or hygiene items can quickly cause plumbing to clog, leading to sometimes difficult and costly fixes that can leave your holding tank (and boat) out of commission.
  • Sometimes: marine black water tanks need replacing. Boat owners often choose to buy a new holding tank whenever it was neglected by a previous owner, when improper activity has caused damage, when extended use calls for its replacement, or when they want to upgrade to a larger volume tank.

*Common marine sewage laws and regulations:

  • Boating vessels with a toilet installation must have that toilet fitted to a full Marine Sanitation Device, where Type III designs are most common but other treatment methods can be acceptable.
  • A general guideline at the time of this writing, untreated waste is illegal for release within three (3) miles of coastal shores and within all inland waters such as lakes and rivers. This may vary by region.
  • Certain protection areas are prohibited discharge zones even for treated wastewater. Always verify your sailing zone prior to disposal.

how to clean water tanks on sailboat

Takeaway | Cleaning a Marine Holding Tank

Caring for your boat’s onboard septic tank may not be the most pleasant responsibility, but you, your shipmates and your holding tank will thank you when it is properly maintained. And thankfully, if regularly maintained, caring for a marine holding tank can be a fairly simple and easy process only needing to be pumped, rinsed and flushed. In most cases, tank treatment additives are not necessary and only assist in making tank maintenance easier. Deep cleaning of a tank is mostly reserved for when upkeep has been overlooked or in neglected tanks.

We hope our how-to guide has helped in better understanding your boat’s blackwater holding tank and how to clean it. If you are in need of a replacement tank, we provide a range of long service, top-of-the-line marine holding tanks made by some of the industry’s leading manufacturers and suited for most vessels up to 280 gallons. If you have any questions, comments or needs, don’t hesitate to contact us . All the best, and as always: happy boating!

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About Alek Eccles

Alek Eccles is a technical writer and professional content creator. Education in english and science; experience in chemical storage, standards; pharmaceutics; environmental assessment and stewardship; governmental regulations and codes. Alek seeks to bring increased understanding to technical, chemical, and biological industries, systems, and concepts; rainwater harvesting; plastics/thermoplastics; as well as containers used for general storage, handling, and transport.

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Cleaning the holding tank sludge

  • Thread starter sailcapt340
  • Start date Jul 15, 2014
  • Hunter Owner Forums

sailcapt340

sailcapt340

Has anyone any tips for cleaning out the sludge at the bottom of the holding tank? A recent clog in the waste line from the toilet had me removing the line from the tank to be able to snake out the line properly. Now all is running well. On the other hand, the tank indicator does not fall completely to the zero level, which has me believing that the same hard sludge is at the bottom of my tank, keeping the float from falling to the bottom. The macerator runs fine and will discharge any waste from the tank, but I still feel there has to be a build up at the bottom. I do flush the tank every time I pump out, but is that enough to keep it clean? Thanks for any tips or procedures.  

Just a purely uneducated, untried thought here, but I recently saw an ad on TV for RID-X. Apparently they now make a version of their product for RVs. I got to thinking, why wouldn't this work in a marine holding tank? Of course like I said, I haven't done any research, and for all I know this stuff might eat away at a marine holding tank or something else bad. Has anyone else heard of this?  

py26129

sailcapt340 said: Has anyone any tips for cleaning out the sludge at the bottom of the holding tank? A recent clog in the waste line from the toilet had me removing the line from the tank to be able to snake out the line properly. Now all is running well. On the other hand, the tank indicator does not fall completely to the zero level, which has me believing that the same hard sludge is at the bottom of my tank, keeping the float from falling to the bottom. The macerator runs fine and will discharge any waste from the tank, but I still feel there has to be a build up at the bottom. I do flush the tank every time I pump out, but is that enough to keep it clean? Thanks for any tips or procedures. Click to expand

Sailvayu

First thought is the sending unit is stuck and will not go all the way down. I would pull that and clean it first. I like the rid-x idea as well and have been thinking of trying that myself. I did not know they had it for RVs so I will have to look into that.  

Pulling the sensor I did plan on pulling the sensor out this week to just check that it was moving free. That will give me the opening to see in the tank at the same time. I didn't know about the Ridx either. Might be something.  

John T1594

Sludge I'm not sure where I found this but it was filed away in case I ever needed it: To remove holding tank sludge build-up: Add two cups of Calgon Water Softener to one gallon of hot water and pour into tank. Add one cup of liquid laundry detergent to one gallon of hot water and add that to the tank. Let sit for several hours, then fill the tank with water and let that sit for a few more hours. Pump out tank and rinse a second time. It probably would not hurt to slosh the tank around a bit with a trip out and back.  

Scott B

Best advise from Peggie Hall http://forums.hunter.sailboatowners.com/showthread.php?t=107140&#post618140 and her book has lots of good advise. http://shop.sailboatowners.com/prod.php?53615  

Rocket1

Not a fun task.... The PO of our boat wasn't too regular about pumping out the holding tank, so we inherited a tank with a significant "hockey puck" in it, as well as a level guage that didn't work. I pulled the sending unit and cleaned it (was serioiusly plugged up), and then tried a multitude of chemicals and snake oils in an effort to break up the "puck". None with any notable success. I finally took the plunge (not literally) and installed a 6" inspection port in the top of my holding tank. This allowed me space to get into the tank with a hose nozzle to break up the gunk. While I sprayed and held my breath, the Admiral held the pump out nozzle on deck. While a ton of work, I can say that about 200 gallons of water later - the tank was clean. I still have to replace all of the hoses, but that's for another day.  

splax

Hello, I think coffee grounds might be a good thing to put down the waste outlet They seem to do a good job on the toilet bowl at home, when I am cleaning the French press. I think the acidic nature of the coffee is the thing. I am thinking if they scrubbed around while underway that would be a good thing. I tried to contact Peggy to run it by her, but had no luck.  

I think adding extra solids like coffee grounds to your tank is a poor idea!!!!!!!  

I thought some of those enzyme based additives worked on the hardened residue that comes from long deferred maintenance. Those bacteria can be voracious little devils. Maybe a little steak sauce to encourage them?  

thinwater

Flush with more water volume. Folks flush until the bowl is empty, but really need another 6-10 strokes after that. The extra water really helps. This is just a matter of following the instructions. Nitrate and enzyme based products really help. I did 3 years of side-by-side testing for PS, and the tanks with the treatments contained nothing that didn't slide right out. Those with no treatment, and worst those that had used veggy oil on the head, contained sludges. And Peggy's advise is sound, as always. Conservative, but effective. Better than forum chatter!  

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IMAGES

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  3. How to Clean a Boat Water Tank (with Pictures)

    1 Turn on your boat's water pump. Before you clean your boat's tank, you'll need to empty out the stale water inside. If your water pump isn't already on, turn it on so that you can drain your tank completely. [1] The location of the pump and water tank varies from one boat to another.

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    Plumbing Keeping Water Clean and Fresh Good old bleach is great, but treatment tabs have advantages. By Drew Frye - Published: June 16, 2015 Updated: February 10, 2023 27 In the first part of our three-part series covering onboard water quality, we discussed protecting the tank with basic filtration and securing the tank vent.

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    #1 hey everyone, getting ready for splashing the boat, just changer the water pump/faucet to electric, and changed all the hoses at the same time, the old hoses were black from sitting for the last 7 years, what would be the correct way to sanitize the water tank and system?

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    Get more information on Checklists for Sailors here: https://sailingbritican.com/product/checklists-for-sailors-paperback/PLEASE subscribe to my channel and ...

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    Mix in your cleaner and fill the tank with enough water to dilute the cleaner to an appropriate amount. You can then turn off the pumps and the taps to allow this cleaner some time to go to work. Leave it overnight for the best results. Shop Cleaning Products from BoatLIFE Drain and Rinse

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    Use an eighth of a cup of bleach for each 10 gallons in the system; add the bleach to a gallon of fresh water and mix the solution. If the boat has aluminum water tanks, you may choose a non-chlorine sanitizing product. Pour the mixture into the water tank, and then fill the tank.

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    Holding tank maker Dometic/Sealand recommends that boat owners empty the tank, then fill it about halfway with fresh water, and add 8 ounces of a liquid, bleach-free, biodegradable laundry detergent to the water before getting underway, preferably for a few hours of sailing in choppy conditions.

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    Don a sanitary rubber glove and swab your finger across the inside of the tank. If it feels slimy or emits an odor, the tank's interior needs to be scrubbed with detergent, rinsed and sanitized. | |The bottom right hose in this image relies on steel wire reinforcement, which unfortunately is rusting. Seek other alternatives.| Advertisement

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    The best way is to answer the call of nature in the sea. Take a leisurely swim far out to sea, fully relax as you do, and then casually relieve yourself. The bidet is all around you, so there's no need for toilet paper. Then swim back to the boat just as relaxed.

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    To do this, add a purifying tablet to a full water tank and leave to activate for the advised time period. Once purification has occurred, turn all the taps on and drain the system as much as possible. This will ensure purification flows through the system.

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    Take the boat for a short trip, about 30 minutes, to churn the hot water inside the system, which helps loosen the stickiness of sticky filth inside. Or try any appropriate way to shake the tank. Drain the tank completely through every faucet. Drain it as fast as you can. Do it while the boat is moving if possible.

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    1. Mild Soaps and Non-etching Detergents: Non-ionic detergent such as "Joy" a. If a mild soap or detergent is gentle enough o be applied with bare hands, it can be safely used on aluminum without spot testing first. b. Automatic dishwasher detergents should be always spot tested first.

  18. How to clean inside of holding tank?

    Pump out, also run some of the dietergent through any macerator pump. Fill tank again with clean fresh water...pump out and dump again. That oughta do it. A cupful of liquid detergent down the toilet 2-3 x/season will prevent the need to do this in the future. Tank should be thoroughly flushed out with clean water 2-3 x/season--and especially ...

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    Both cases can often be fixed using a plumber's snake. (3) Sludge layer remains after flushing the holding tank can be a result of too much time between maintenance. Sometimes filling the holding tank with clean water and agitating the water by chopping the boat can break up materials for their removal.

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    However, with the nylon hose tees you'll also need six stainless steel hose clips at a cost of $1.99 each, bumping the total price tag for the "low-cost" solution up to $33.21. West Marine lists Whale's 15mm tubing at $1.49 per foot (blue), compared to food-grade reinforced 5/8in PVC hose at $1.79 per foot.

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    To remove holding tank sludge build-up: Add two cups of Calgon Water Softener to one gallon of hot water and pour into tank. Add one cup of liquid laundry detergent to one gallon of hot water and add that to the tank. Let sit for several hours, then fill the tank with water and let that sit for a few more hours.

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