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11 Easy steps to Sanitize the RV Fresh Water Tank

| Updated Jun 21, 2023

Once a year every RVer needs to sanitize the RV fresh water tank. Here's how:

Your RV's fresh water tank can get stale and sour and a little sanitation will ensure good tasting water all season.

In fact, we do ours about three times a year… in the spring when we de-winterize, in early summer when the weather starts getting hot, and late fall, just before we run antifreeze through the plumbing.

Why you should sanitize the RV fresh water tank

Because you don't want to get sick. Fresh water sitting in a tank can breed all sorts of organisms, many of them unhealthy. Generally, the experts tell us that you should not leave water in the tank for more than two weeks before it starts to get skunky.

In the summer, when those tanks can really heat up, my recommendation is change out that water every week. Don't let it sit there unused between trips for long periods of time.

But even after emptying it and refilling it, traces of those unhealthy microorganisms can be left as a residue in the tank. You need to kill them and the best way to do that is by sanitizing your tanks.

At the least, unsanitized water will taste sour. It may smell. It will be increasingly distasteful. You could get diarrhea… or other unpleasant and potentially even serious diseases. So sanitize those tanks!

Conflicting advice about the best way to sanitize the RV fresh water tank

You will get all sorts of advice about this if you start searching around.

For example, the manufacturer of one of the RVs weve own, advised its customers when winterizing the RV to put antifreeze in the fresh water tanks.

That is not good advice.

photo of an rv fresh water tank being drained
There is no need to put antifreeze in your fresh water tank because you empty that tank as part of the winterizing process. When I sanitize the RV fresh water tank in the spring as part of the de-winterizing process, I fill and drain the tank several times just to make sure any gunk in the tank is out before I put some bleach in it.

I admit, we have done so, as suggested by the manufacturer of one of our previous RVs. But think about it. That advice is not really necessary. There's no need to do so since there is no water in it after you winterized it. There is no water in there to freeze.

And if you have ever tried to get the antifreeze taste out of your fresh water tanks at the beginning of the camping season, you'll understand why we cursed the manufacturer who recommended such a thing.

Step-by-step instruction on how I sanitize the RV fresh water tank

photo on how I sanitize the rv fresh water tank
I sanitize the RV fresh water tank with good old household bleach. I use about 3 ounces for every 25 gallons of water.

The steps are pretty simple. In all fairness, I am the first to admit that I am  a bit of a fresh water snob so, personally, I fill and drain my fresh water tanks more than most people do.

All of these 11 steps are part of the de-winterizing process.

  1. Fill and empty the fresh water tank. This just rinses out any residues that could affect the taste of the water. So fill it and then empty it. 
  2. After that fill and drain, refill up the fresh water tank with clean water.
  3. Go inside, run the galley and bathroom faucets until the “pink stuff” (antifreeze) was out of the pipes and then let it run clear for a couple of minutes. You will also want to also do this with the inside and outside (if you have one) shower.
  4. Outside again, once again drain and then refill the fresh water tank, this time adding about three ounces of bleach for every 25 gallons of capacity n your fresh water tank. Let it sit like that overnight.
  5. The next morning, go back inside the coach and again run the faucets and flush the toilet and shower with lots of water, getting some of that sanitized water into all the pipes. 
  6. Drain that fresh water tank one more time
  7. After doing all of that, drive the RV to a location where you can dump the black and grey water tanks so you could start out with clean, empty storage tanks.
  8. Back in the driveway, fill the fresh water tanks one last time, but about half way so you have enough on hand for your traveling needs, but not so much as to add unnecessary weight while on the road.
photo of clear 20 inline water filter
As part of the way I sanitize the RV fresh water tanks, I replace my inline water filter at the start of each season. I do the same thing about midway through the summer. The filter I use is the Clear 2O Inline Water Filter

9) Something else I do: I change the online filter that I put on the hose. I use the Clear 2O Inline Water Filter between the hose and the water intake. I change this once or twice a year, depending on use. It does a great job removing or reducing bad taste, odors, chlorine and sediment in drinking water. I also replaced the filter on the instant-on clean water tap by the sink.

10) Before heading out, I run a glass of water through the galley faucet and take a sample drink, making sure there is no bleach or antifreeze taste. If there is, I just drain and refill once more.

Admittedly, I drain and empty a lot. If you are thinking that's a bit much, you can skip one or two fill and drain cycles

photo of fresh water hose
We get a new “water safe” fresh water hose at the start of each season.

11) Besides the water filter, at the start of every season as part to the sanitization process, I also replace the fresh water hose I use to fill my fresh water tank or hook up to the city water faucet at a campground. Never use a garden hose to put water in your RV. The hose needs to be marked “water safe.” A garden hose is filled with sediment and microorganisms. This is the one we get every spring.

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Mike Wendland

Published on 2020-12-21

Mike Wendland is a multiple Emmy-award-winning Journalist, Podcaster, YouTuber, and Blogger, who has traveled with his wife, Jennifer, all over North America in an RV, sharing adventures and reviewing RV, Camping, Outdoor, Travel and Tech Gear for the past 12 years. They are leading industry experts in RV living and have written 18 travel books.

5 Responses to “11 Easy steps to Sanitize the RV Fresh Water Tank”

June 20, 2021at3:22 am, Samantha Nichols said:

The bleach/water solution won’t magically sanitize your system. It’ll take some time, about 12 hours or so, to do a thorough, adequate job. An easy method would be to let it sit in your freshwater tank overnight. Therefore, you won’t have to think about it.

June 13, 2021at3:27 am, Samantha Nichols said:

Sanitizing your RV tank effectively will require a bleach solution. You’ll need to add a ¼ cup of bleach for every 16 gallons of water within your freshwater RV tank. This measurement will equal one ounce of bleach per eight gallons. But please don’t add the bleach right into your freshwater tank. It needs to be diluted first with a gallon of water for each ¼ cup of bleach. The bleach will be a little too potent and render your freshwater tank unusable without it. Experts recommend sanitizing your RV’s water tank at least every six months.

January 04, 2021at9:41 am, Harold Ross said:

My fresh water tank had the outlet fittings on the side of the tank, so because of the tank radius and fittings retainers, there is always about 1.0 to 1.25 of water remaining in the tank. Hence 2 problems, how to keep it from freezing because I agree with you that I prefer not to drink anti freeze and with this set up all that can be done is keep diluting any thing put in the tank, even stale water, bleach, anti freeze or what ever. I would like to know how to best maintain this type of fresh water tank? I investigated blind bulk head fittings to put into the top for sucking out the water, but wasn’t satisfied with that solution either, tried to remove tank, but it was too big for access door, so what is your recommendations

December 21, 2020at6:44 pm, Conrad said:

I am curious why you would not just sanitize the fresh water hose instead of getting a new one. Is there somewhere that shows that the hose material deteriorates over one season?
The hoses that I have seen do not have a cap when it sits on a shelf so debris/anything could get in before your purchase.

December 21, 2020at5:20 pm, Suzanne DallaBetta said:

On step 9 when you are replacing the water filters, you said you also replace one near the sink, was this the same filter, or something different/smaller? Thanks.

Love your blog , thanks for all your great articles and info!
Merry Christmas!
San Clemente, Ca.

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