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Sanitizing Your Holding Tanks & Removing Algae

April 06, 2020

Learn how to sanitize your holding tanks - Unique Camping + Marine


  1. It's very important to sanitize your RV fresh water tank at least once a year to prevent contaminants or algae build-up. These contaminants and algae can be very harmful to your health!
  2. Because we are dealing with the RV fresh water tank and not the black or gray tanks, it's not as important to avoid using anti-bacterial products. In fact, bleach and anti-bacterial products are pretty much your only option for sanitizing your tanks.
  3. Follow the step-by-step guide below to sanitize your RV fresh water holding tank using either bleach or an anti-bacterial product. 
  4. Often, people will complain that the water from their fresh water tank tastes gross. There are ways to freshen the water. We will be covering this topic in a future article, so check back!

If you’ve been RVing for any length of time, it’s likely that you’ve heard a whole lot about RV holding tank maintenance. In fact, we have written many articles about how to properly care for your holding tanks using The Unique Method! But there’s a topic that often gets pushed to the side when it comes to properly maintaining your tanks: how do you deal with dirty, contaminated fresh water and algae build-up in your fresh water holding tank? 

In all honesty, algae build-up is relatively unlikely, because algae needs some form of sunlight in order to grow. However, this is possible if, for example, your RV has clear water lines. It is very important that you sanitize your tanks regularly, because this is your drinking water, and no one wants tainted drinking water! It's also important to prevent algae blooms in your fresh water tank as it can be very harmful to your health! In this article, we’ll provide you with a step-by-step guide to sanitize your RV fresh water tank using bleach and/or an anti-bacterial product!

Using Bleach or Anti-Bacterial Products

Okay, we know what you’re thinking: how can they recommend bleach and anti-bacterial products when every other article says not to? It’s a fair question. 

There are three things to consider here: 

  • We are dealing with the RV fresh water tank, not the black or gray tanks, which means that the rules are completely different. In your black and gray tanks you WANT a thriving culture of bacteria (aided by a high-quality, bacteria-based holding tank treatment) to assist in waste breakdown and odor elimination. In your fresh water tank you DO NOT WANT any bacteria as this is the source of your drinking, hand-washing, and bathing water.
  • If you want to thoroughly sanitize your fresh water tank, ultimately the only way to do this is by using bleach or anti-bacterial products. These sorts of products are pretty much the only option to sanitize the fresh water tank in your RV, but don’t worry; you’re going to make sure the tank is completely clean before you use it again!
  • In addition to using chemical cleaners, like bleach, to remove algae blooms, you may also want to consider using a high-quality algaecide. You can typically find these products at your local hardware store or swimming pool supply store. Just make sure you fully disinfect and sanitize the tank after using these products (more on that below).

Guide Continued Below

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A Step-by-Step Guide

To sanitize your RV fresh water tank with either bleach or another anti-bacterial product, follow these checklist steps:

  1. Turn off your hot water heater. Wait a few minutes before proceeding to the next step. 
  2. Locate the outside compartment where your water heater is placed and open the pressure relief valve. 
  3. Empty your water lines. Since algae and contaminants can build-up in the water lines of your RV, you’ll need to start by making sure they’re empty. You can do this by locating and opening your low-point water drainage valves. You may also need to open the drain on the fresh water tank itself. Your RV owner’s manual should tell you where these valves are located.
  4. Once your water lines and tank are totally empty, it’s time to mix your bleach solution. For every 15 gallons that your RV fresh water tank holds, you should mix about 1/4 cup of bleach with a few gallons of water in a bucket. 
  5. If you choose to use an anti-bacterial product to sanitize your tank, follow the product directions to determine how to mix your solution. 
  6. Carefully pour your solution into your fresh water tank. Using a funnel might make this a whole lot easier! 
  7. After you’ve poured your bleach/anti-bacterial solution into the tank, fill the tank with fresh water until it is almost full. 
  8. Run water through all of the sink faucets, one at a time, to fill the lines completely. Do not run the faucets so long that you empty your fresh water tank! You should smell bleach coming from each faucet. 
  9. Some RVers find it helpful to take a short drive once every water line is filled with the bleach/anti-bacterial solution. This can help to slosh the water around.
  10. Let the solution sit in your water lines and fresh water tank overnight. 
  11. After you’ve let the solution sit overnight, drain the fresh water tank and water lines into a proper waste receptacle. 
  12. Completely fill your tank with fresh water and turn on your faucets, one at a time, to completely flush your lines so only fresh water remains in the lines. You should repeat this step until there is no longer any bleach smell in the tanks or from any faucets.

Continued Maintenance:

To help prevent contaminant and algae from building up in the first place, you should sanitize your tanks every six months to once a year. Because algae is relatively unlikely in fresh water tanks, it should be fairly easy to prevent if you keep up on regular sanitations. For example its a great idea to sanitize your tanks when you winterize. Simply complete the steps given above, and you should have an algae-free RV fresh water tank! 


Needless to say, proper maintenance of all your RV holding tanks is very important! Not only can it fix existing issues, but it can help to prevent future issues as well. We hope that this guide has been helpful as you sanitize your RV fresh water tank! We would love to answer any questions, concerns, or comments you might have about this topic! Please reach out to us for help.

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