How-To Properly Clean Your RV Fresh Water Tank

While we know our RV’s black and gray holding tanks are dirty (they contain waste, after all), our freshwater holding tanks need regular and thorough cleaning too. Here’s the easy process to get your fresh water holding tanks so clean you can drink out of them. 

You can use this technique on any truck camper, travel trailer, fifth wheel, or motorhome. Heck, you can use this procedure on your boat or yacht as well!

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We’ve asked our friend Jim Tome of Kleen Tank for his professional advice by writing this guest blog. We’ve met Jim at a Heartland Owners Club Rally a couple years ago and he’s been instrumental on setting the record straight on tank flushing, cleaning and maintenance information. Who better than to get it right from the source. So, we thank Jim for taking the time to share with us the proper way of doing this.

Yuck, mold!

Quite simply, it’s mold. The inside of all of your RV’s holding tanks is an environment — especially in the summer or during other hot, humid weather — ripe for the growth of molds and odor-producing bacteria. 

But it’s also a dirty fresh water holding tank that is also likely contributing to the problem. 

If you use your fresh water holding tank at all, you need to sanitize it. How often? At least twice a year, no matter how often you use your RV. We like to do one right after we’ve de-winterized the RV and another mid-way through our RVing year. 

If you are a full-timer or use your RV and it’s fresh water holding tank pretty frequently, then plan on sanitizing that tank three to four times a year, at a minimum. How do you do that? 

Always On Liberty Disclaimer: Before getting started, we recommend you do not wear your favorite clothes when doing this. Also, you may want to wear some PPE (personal protection equipment) such as rubber gloves and safety glasses. Because, since we tell you that and you hurt yourself, you can’t take us to see Judge Judy.

The process is pretty simple…

You are basically going to get a diluted mixture of household bleach into your fresh water holding tank, pump it into throughout your RV’s water system, let it sit for a period of time, then pump it all out. 

The active sanitation and disinfectant ingredient in bleach is sodium hypochlorite. It’s been used for centuries as a disinfectant and bleaching agent. Common, household bleach is a very diluted solution of sodium hypochlorite and, mostly, water. While not toxic, it can be very corrosive, even eating completely through stainless steel if left too long. It’s perfect for destroying bacteria, molds and mildews, and even most viruses. 

To sanitize the water system in your RV, use a quarter cup (two ounces) of household bleach for every fifteen (15) gallons of water your fresh water tank holds. Some instructions will say to mix the bleach in a bucket or other container with fresh, potable water and then pour that into your fresh water holding tank. We think that makes a big mess that results in bleach on our clothes, hands, the side of the RV, and on the ground. 

There’s a better way… 

Using your potable water hose (NOT a garden hose! — we’re talking about the special white or blue water hose intended specifically to bring park or city water to your RV from the spigot at your site), pour the appropriate amount of bleach (quarter cup (four ounces) for every fifteen (15) gallons of capacity in your fresh water holding tank into the empty water hose, connect the water hose to your RV’s fresh water tank inlet, and then fill the fresh water holding tank with potable water (which will also now have bleach in it). 

Once full, briefly turn on every water tap, the shower head, and even flush the toilet in your RV until you detect a strong and distinct bleach smell from each water source. This ensures that the pipes and other fixtures have bleach in them; your entire fresh water system needs to have this mild bleach-water solution in contact with it. 

The guideline is to let your RV’s plumbing system and fresh water tank (now nearly full of bleach-y water) for a minimum of four (4) hours. We like to leave it overnight. 

Once that time period has passed, pump out the water from your RV’s fresh water tank through the waste disposal system (from each water tap, the shower head, toilet, etc.), into the holding tanks and then empty them thoroughly. We recommend that you fill each of your holding tanks again with fresh, clean water and then empty it again to remove any remaining bleach solution. 

Refill your RV’s fresh water tank with clean, potable water. No bleach this time. Let it sit for an hour. Then pump it all through the system again and empty those holding tanks one last time. Your RV’s water system is now sanitized. Now, wasn’t that easy?! 

Some precautions…

Splash-less bleach is a little thicker than regular, household bleach. The active ingredient, sodium hypochlorite, only has a 1-5% concentration, not enough to sanitize and disinfect, as the label on the bottle will warn. Use regular, household bleach (that doesn’t say “splash-less”) instead. 

Household bleach, as we mentioned, can be extremely corrosive. It’s important to wipe down any surfaces that it may have spilled on with water or ethanol and definitely avoid letting bleach stay in contact with delicate metal instruments or structures (such as your holding tank’s sensor probes) for very long. 

Bleach can also damage rubber or plastic parts and surfaces, such as water supply and waste disposal plumbing pipes, holding tank seals, and other soft, delicate parts in your RV.

Very Important!! Rinsing away and disposing of the diluted bleach-water solution used to sanitize your RV’s fresh water holding tanks is a critical last step. 

Bleach also degrades quickly, especially when exposed to sunlight. Always store bleach in a cool, dry environment in thick, opaque plastic (like the one it comes in!) or glass bottle. Never mix bleach and ammonia-based cleaners. Doing so will create toxic chloramine gases and an explosive called nitrogen trichloride. Yikes! 

So, that’s a wrap! Now you know how to properly clean and sanitize your RV’s water tank and system.

About our Guest Author

Jim Tome, owner of Kleen Tank, an Authorized All Pro Water Flow dealer, has been an RVer for over 15 years. His company provides RV holding tank cleaning services throughout the U.S., but mostly in the Midwest. He posts weekly articles on RVing, tips and advice, and relevant topic on the blog at He attends RV rallies throughout the year, giving seminars, answering questions, and teaching RVers about their RV’s holding tanks and waste handling systems. 

12 Replies to “How-To Properly Clean Your RV Fresh Water Tank”

  1. I was just wondering, is it 1/4 cup of bleach (2 oz) or 4oz (1/2 cup) per 15 gallons of fresh water?
    Thank you!

    1. Brenda, thank you for following our blog. The answer is: “To sanitize the water system in your RV, use a quarter cup (two ounces) of household bleach for every fifteen (15) gallons of water your fresh water tank holds.” Hope that helps! -Dan & Lisa

    1. Hi Jaime, thanks for following along and taking time to read our blog. Anytime you flush your tanks, it should be at a designated dump station or sewer connection at a campground, RV park, rest stop, etc. Never dump on the ground where ground water may lead to rivers, streams, lakes or the ocean. Hope that helps! -Lisa and Dan

    1. Hi Mike, thanks for asking. The only bleach is through your fresh water tank when you sanitize. There are no special solutions for your hot water tank specifically. -Dan

    1. Hi Aaron, good question. Hook up your fresh water hose (white one) to your RV’s fitting. Before hooking up the other end to the water spigot, carefully pour the prescribed amount of bleach into the hose using a funnel. Then, being careful not to have it spill out while hooking up the hose to the water spigot. Then turn on the water on. Hope that helps! Safe travels!

  2. I want to clean the RV’s water tank without detergents. I also have a way to clean the water tank, you can read it:
    Step 1 – Empty the water tank and then check the anode rod. If it is in a bad condition, like if it is heavily corroded or has clear signs of deterioration, then you need to replace it first before you continue with the next steps.

    Step 2 – If the anode rod is still in good condition, use a rinsing rod to flush out any dirt from inside the water tank.

    Step 3 – If you live in an area with hard water, the inside of the hot water tank might have gotten clogged up with all sorts of mineral deposits. To get rid of these mineral deposits, add a couple of tablespoons of white vinegar into a gallon of water and then pump it into the water heater tank.

    Step 4 – Another way to go about this is to open the pressure release valve and pour the water and vinegar solution through the top poof of the heater using a funnel. Wait a couple of minutes and then drain the water tank completely.

    1. Hi Samantha, you’re suggestions are pretty much everything we’ve posted in the blog, so we must be doing something right. Not too sure about Step 4. I’m curious, are you a certified RV technician? Thank you for reading.

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