How to Clean and Sanitize RV Fresh Water Tank

RV owners should periodically clean and sanitize your RV fresh water tank. If you don’t, there’s chance that you and your family will get sick from mold and bacteria growing inside the tank. We’ll show you the correct and safe water tank cleaning process to ensure your RV’s potable water is safe.

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How to Sanitize your RV Water Tank
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We’ve asked our friend Jim Tome of Kleen Tank for his professional advice by writing this guest blog. He’s instrumental on setting the record straight on black tank cleaning and flushing  and general RV tank maintenance.

How to Clean and Sanitize your RV Fresh Water Tank

What’s growing inside your RV’s water tank?

Quite simply, it’s mold.

The inside of your RV’s water tank presents the perfect environment for mold and odor-producing bacteria to grow; especially during warmer temperatures.

Mold in your RV Water Tank

If your fresh water tank is already dirty from not maintaining it’s sterility, that’s likely contributing to the problem.

How often must you clean your fresh water tank?

If you use your fresh water holding tank at all, you need to sanitize it at least twice a year, no matter how often you use your RV.

It’s recommended to clean it right after you de-winterize your RV, and another halfway through your RVing season.

But, if you’re a full-time RVer or use your RV fresh water holding tank frequently, sanitize it at least three to four times a year.

Before we get into the actual water sanitization process, we’ve got to talk about preparations and precautions.

Fresh water tank cleaning and sanitizing preparation

Prior to cleaning and sanitizing your RV’s water tank, we highly recommend parking your motorhome or towable RV at a full-hookup campsite. You’re going to be flushing your water system. Which in turn, will fill your RV gray tank. So, make certain your gray tank valve is open during this process.

RV Fresh Water Tank - PPE

Also, we recommend you wear clothes you don’t care about. We also leave it to the user’s discretion to wear rubber gloves to protect your skin. And, put on safety glasses to protect your eyes from splashes.

Sanitation precautions

Splash-less bleach is a little thicker than regular, household bleach. The active ingredient, sodium hypochlorite, only has a 1-5% concentration. As the label on the bottle will warn, it’s not enough to sanitize and disinfect.

We highly recommend using regular, household bleach instead. Household bleach, as we already mentioned, can be extremely corrosive. So, it’s important to wipe down any surfaces that it may have spilled on with clean water or ethanol.

You’ll definitely want to avoid letting bleach stay in contact with delicate metal instruments or structures (such as your holding tank’s sensor probes) for very long. 

Also, bleach can damage or degrade 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.

This is precisely why rinsing and disposing of the diluted bleach-water solution used to sanitize your RV’s fresh water holding tanks is so critical.

Lastly, household bleach degrades quickly; especially when exposed to sunlight. Always store bleach in a cool, dry environment in thick, opaque plastic (like the container it comes in!) or glass bottle.

And NEVER mix bleach with any ammonia-based cleaners. Doing so will create toxic chloramine gases and an explosive called nitrogen trichloride. 

So, now that we got that out of the way, let’s get down to the nitty gritty of cleaning and sanitizing your fresh water tank.

How to clean and sanitize your RV water tank

The cleaning and sanitizing process is quite simple. You are basically going to get a diluted mixture of household bleach into your fresh water holding tank.

Then you’re going to pump it throughout your RV’s water system. You’ll need to allow it to sit for a couple hours. And then allow it to drain into your gray tank and through your RV’s sewer hose into your campsite’s sewer hole.

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. Really, it’s mostly water but with traces of the chemical.

While not toxic, it can be highly corrosive. It can completely eat through stainless steel if left too long. But, it’s perfect for destroying bacteria, molds and mildews, and most viruses. 

To sanitize your RV’s water system, use a quarter cup (two ounces) of household bleach for every fifteen (15) gallons of water that 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 mixture into your fresh water holding tank.

RV Fresh Water Tank - No

However, that will just make a big mess that can result in bleach coming in contact with your clothes, hands, the side of the RV, and even on the ground.

But there’s a better way.

Instead, using your potable water hose, pour the appropriate amount of bleach (quarter cup or four ounces) for every fifteen (15) gallons of capacity in your fresh water holding tank into an empty water hose. Then, connect the water hose to your RV’s fresh water tank inlet. Finally, fill the fresh water holding tank with potable water (which will also now have bleach in it). 

We recommend NOT using a regular garden hose. Only use the special white or blue water hose intended specifically water transfer from the spigot at your site to your RV.

RV Fresh Water Tank - Blue Water Hose

Once full, briefly turn on every water faucet in your RV. This includes the shower head and even flush the toilet until you detect a strong and distinct bleach smell from each water source.

RV Fresh Water Tank - Bathroom Faucet

This ensures that the pipes and other fixtures have bleach in them. Your entire RV fresh water system needs to have this mild bleach-water solution in contact with it. 

We recommend that you let your RV’s water system and fresh water tank (now nearly full of bleach-y water) set for a minimum of four hours. Or, you can leave it set overnight. 

RV Water Tank Maintenance

Once the time 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 black and gray tanks. Then, open your sewer valve to allow the solution to go through your sewer hose into the campsite sewer.

We recommend that you fill each of your holding tanks again with fresh, clean water. Then, empty it again to remove any remaining bleach solution. 

Once your RV’s fresh water tank is completely empty, refill it with clean, potable water only. Let it sit for an hour. Then pump it all through the system again and empty your RV’s holding tanks one last time. Your RV’s water system and fresh water tank is now sanitized.

Now, wasn’t that easy?! 

So, that’s a wrap! Now, you know how to properly clean and sanitize your RV’s water tank and system. We hope this self-help tutorial has helped you understand the process of cleaning and sanitizing your RV’s fresh water tank and fresh water system.

RV Fresh Water Tank - Child Drinking Water

About our Guest Author

Jim Tome of Kleen Tank

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. 

Relatable articles – RV upgrades, modifications and improvements:

Clear Source RV Water Filter System

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RV Upgrade: Our Fifth Wheel Anderson Kantleak RV Water Service Panel

Plumbing and Drain Maintenance

Valterra RV Sewer Hose Storage


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17 Replies to “How to Clean and Sanitize 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

  2. Where do you suggest we dump the bleach diluted water from the gray tank after we flushed the lines? 🙂

    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

    2. Always dump your wastewater into a designated dump station or sewer for proper disposal. Although the bleach would deteriorate in the sunlight, It’s never a good idea to pour bleach onto the ground. It will kill or make sick everything it comes in contact with until it breaks down. This includes essential bacteria, fungi, and more.

    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!

  3. 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.

  4. How long is the water that you have left in the fresh water tank OK for continued future use after the RV has been standing idle?

  5. Cleaning the RV fresh water tank is necessary to eliminate any potentially hazardous pollutants that may be present. Ingesting algae and dangerous bacteria can raise the likelihood of health problems such as vomiting, fever, and gastroenteritis. Thank you for sharing your experience.

  6. Thanks for these helpful tips. Cleaning the RV holder tank sensors is an essential skill for all motorhome owners.

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