Using an RV fresh water tank is a relatively simple matter. How to fill it, how to hook up to city water, how to monitor how full it is, how to keep it clean – these are all pretty straight-forward processes. But there’s one important piece of information that often gets overlooked, and that is how long to keep fresh water in an RV tank.

If water sits in a tank for too long, it could cause a host of issues including unsafe drinking water. To learn how to avoid that unhealthy situation and more, keep reading!

How Long Can You Keep Fresh Water in Your RV Tank?

Two weeks is the simple answer to how long to keep fresh water in an RV tank IF you aren’t using the water and refilling during that time.

How long to keep fresh water in RV tank
When water sits unused in a tank, it can become unsafe and therefore undrinkable.

If you use all your fresh water and refill your tanks every week or two, there shouldn’t be issues as long as you keep a clean tank. But, when water sits unused in a tank, it can become undrinkable.

Let’s look at why this happens and what you can do about it:

Does Fresh Water Go Bad in an RV Fresh Water Tank?

Believe it or not, water can “go bad”. If you keep water in your fresh water tank for an extended period, not only could it affect the taste of the water, but it may become unsafe to drink.

Why You Shouldn’t Keep Water in Your Fresh Tank for More Than 2 Weeks Without Using

Since your tanks are plastic, water sitting stagnant inside the tank can assume a plastic smell and/or taste. Worse, it can also grow mold, algae, and bacteria.

If you filled your freshwater tank with water from non-municipal sources (think well water), as many of us do, these issues are more likely to develop. The water can become unfit to drink, cook with or shower in, depending on conditions (heat, for example) and how clean you keep your tank.

Using Old Water from RV Fresh Water Tank

How long to keep fresh water in RV tanks also depends on the intended purpose. If you want to use the water just for flushing your toilet, for example, no harm there. But most of us find many other uses for the water in our fresh water tank. In addition to showering and cooking, how about washing dishes, brushing your teeth, or giving pets a drink?

These are important considerations to keep in mind when tending to the condition of a fresh water tank.

How To Keep Your Fresh Water Tank Clean and Keep Water Fresh

How long to keep fresh water in your RV tank also depends on the cleanliness of your tank. If you maintain your tank well by keeping it clean, you have a far lower risk of mold, algae, and bacteria developing.

Use bleach to sanitize your fresh water tank and lines
Routine sanitizing your fresh water tank ensures that the water you store in that tank stays cleaner for a reasonable period of time.

So let’s look at some tips to keep your drinking water safe longer.

Sanitize Your Fresh Water Tank

A critical part of RV living is sanitizing your fresh water tank. Regularly sanitizing the tank ensures that the water you store in that tank also stays clean.

The standard method of sanitizing a fresh water tank is to add a bleach and water mixture. Using a ratio of 1/4 cup of bleach for every 15 gallons of tank capacity, add this mixture to your fresh water tank.

Next, top up your fresh water tank with city water. Then, one faucet at a time, open all your water lines, and run it until you can smell bleach at the faucet.

Let your tank sit for 8-12 hours, then drain the bleach & water mixture out. Then refill the tank with fresh water, and run water up through all the faucets to flush out the lines. To do this, run the water until it doesn’t smell like bleach anymore. You’ll probably need to fill and empty the tank a couple of times to clear everything out, but you don’t need to wait 8-12 hours for subsequent flushes.

After that, fill your tank and use it as normal with confidence.

If you aren’t using your tank, leave it empty until you’re ready to hit the road again, then fill it with fresh water before your trip.

Culligan RVF-10 inline RV water filter
An inline water filter is inexpensive reassurance that the water you’re adding to your fresh water tank is clean.

Use an Inline Water Filter

Another way to keep fresh water in your tank longer is to use only filtered water. An inline unit filters all water entering your RV, removing bacteria or sediment, ensuring your tank has clean water.

An inline water filter is easy to use and inexpensive. Just attach it to your fresh water hose, then fill your tanks as usual.

Keep Your Potable Water Hose Clean, Sanitized, and Separate from Everything Else

Your potable water hose must stay clean; otherwise, you could introduce pathogens into your RV water system. Store your water hose in a compartment separate from items that could contaminate it, especially your sewer hose!

Also, don’t let your fresh water hose lie on the ground. We always connect the male end to the female end to keep the hose sealed up when not in use.

Finally, periodically sanitize your hose by diluting bleach in a tub of water and submerging the hose for about 10 minutes. Rinse it immediately with cold water.

Know the Quality of the Water You Fill Up With

Sometimes you won’t know the quality of water you’re using, so using an inline water filter is critical. If you fill your fresh water tank at home, then you know the quality of the water going into your tank. (As an aside, keep in mind that a full fresh water tank adds a lot of weight to your RV which can impact fuel mileage.)

You can also research city water reports in the area where you’re staying. If an RV park uses a municipal water source, you may find an online report revealing the water quality. Based on these reports you can decide if the water is safe to use. But an inline filter is never a bad idea, especially if you intend to drink the water.

How Often to Sanitize RV Fresh Water Tank

A clean fresh water tank yields cleaner water
Clean water from your fresh water tank is essential for drinking, cooking, washing dishes, bathing, brushing teeth and watering pets.

We suggest that sanitizing your RV fresh water tank every six months is a good rule of thumb. This is especially important if you’re unsure of the quality of a water source you’ve connected to. If you’re on the road constantly and use your tanks often, you might want to do it more frequently.

But the same increase in frequency might be called for when letting water sit without use for long periods of time. And always sanitize your fresh water tank when you take your RV out of storage.

To summarize, how long to keep fresh water in your RV tank depends on several factors. Long story short: Don’t hold water in your tank for extended periods without using it. Keeping a clean tank is essential, as your health may depend on it!

The Ultimate Protection For Safe RV Drinking Water

If you really want to make sure the water on your RV is safe to drink, you can do the same thing we do — install an Acuva! LED water sanitization is used by major municipal water systems all over the world. Acuva’s system miniaturizes that technology for RV use.

Check out our videos about installing and testing our Acuva unit. You can even save 10% on the purchase of any Acuva for your own RV!

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21 comments
  1. I would not recommend using an inline water filter when filling your fresh water storage tank. Most of them remove chlorine. If you do wish to use a filter (to remove particulates), you must add chlorine to your storage tank. Not at the amount used for sanitation, but at an amount suggested to make water drinking safe. There are different formulas for city / well / stream water. Non-chlorinated water (especially in warm weather) is a breeding ground for unhealthy stuff.

  2. Did you know that “splashless” bleach does not have the word “sanitize” on the label? Only the old fashioned bleach does. So, do not use splashless for sanitizing water tanks and pipes.

  3. Thanks for the great article. When draining your fresh water tank where do you typically drain the water? I have a valve that I can open and drain to the ground, but that’s a lot of water. Is there way to to divert that to a sewer outlet (other than running the fresh
    water into the gray tank)?

    1. Hi Mark! Because the concentration of bleach is so low, we normally open the low point drain and allow it to run onto the ground. Alternately, as you mentioned, you can run the water pump and pump it into the sewer outlet via the gray tank, with the gray valve open of course. The only other way we can think of to get the water from the fresh tank directly to the sewer would be to affix an appropriately sized hose to the low point drain outlet of the fresh tank, and run it over to the sewer outlet, which is certainly a viable option. it might require something as inelegant as duct tape to hold it in place, but that would probably work just fine.

  4. Hi & thank you for another great teaching article as always! I look forward to your videos & daily email articles.

    Has anyone added colloidial silver to their tanks? I regularly make my own; so the cost of adding it to so many things is very inexpensive. From the glass of water which keeps my toothbrush disinfected & not exposed to air; from my toilet bowl brush to my diffuser; which sanitizes the air. (I used my diffuser in my rv bathroom to eliminate odors; since odors are bacteria & germs) I deal with fungus & black mold issues from previously living in florida & it is in my bloodstream & so using colloidial silver has become as routine to me as taking my daily vitamins; to keep those pathegens, fungus & mold from affecting my life more than it already has, these last 10 yrs. Colloidial Silver is a God-send.

    1. Hi Joanie. Thanks for the kind words. We’ll be interested to see if anyone else has any experience using colloidal silver to protect/sanitize their tanks. We haven’t heard of using it that way, but have heard/seen a lot about its various benefits. So sorry to hear about your exposure to fungus/mold.

  5. I think you should have mentioned city water vs well water. I guess you can cite several examples of bad city water (i.e. Flint, MI), but generally it is good quality and has been treated and tested. That treatment will assure the water stays fresher longer. Well water can be marginal, as in small amounts of coliform bacteria. I would never keep well water in my FW tank.

    1. Very true John, but in case you missed the mention about well water in the article, it’s not too far from the top:

      “If you filled your freshwater tank with water from non-municipal sources (think well water), as many of us do, these issues are more likely to develop. The water can become unfit to drink, cook with or shower in, depending on conditions (heat, for example) and how clean you keep your tank.”

  6. Excellent tips for keeping our fresh water supply safe. Thanks! Are you guys attending any of the Xscapers convergences this year?

  7. There is one thing you did not mention that might be quite relevant this spring: using RV water system anti-freeze as a sanitizer.

    For the first time we could not use our RV for the winter-in-Canada season. I drained all the tanks then added RV antifreeze to the water lines so that the little bits of water left in the lines and pump would not freeze and cause damage.

    When I get the coach ready for travel again I’m planning on flushing the system for sure; but do you think that I also need to sanitize? I probably will because it seems like an easy and safe procedure.

    Our Acuva filter is great for drinking water and ice (have it plumbed into the fridge) but the bathrooms get water right from the fresh tank. So that’s why I’m thinking that the bleach treatment would be better than just relying on the RV anti-freeze as sanitizer.

      1. Hi John, Peter,

        Yes, you are correct. I just went on-line and re-read the information on the jug because I thought it said something about sanitizing the system. Nope, the word on the jug is “protecting”.

        I was planning on sanitizing the whole system before we head out on the road and you just verified that is an absolutely must do.

        Take care, John

  8. Great article, as always. You mentioned that if one is full-timers, that you might want to sanitize more often. How often do you typically do it? We also have two filters coming in; a 5 micron sediment and a 1 micron carbon block. Second question; you were thinking of adding a water softener to your system, did you ever do that?

    1. Hi Mark! Thanks for the great questions. We typically sanitize twice a year, and have been good with that for the past 18 years. We have never used a water softener, maybe because we grew up with hard water, so it doesn’t bother us. One note… we recommend NOT using a carbon block water filter at the city water connection, but rather only using one at the faucet where drinking water is dispensed. The reason for that is because any chlorine which is in the city water is desirable to be in the freshwater tank, keeping it safe. If you block it before it gets into the freshwater tank, there will be zero chlorine in the tank, so we prefer to leave that filter off the water inlet.

      1. I totally agree. On our class A, I added the 5 micron sediment at the city water source, the house filter (carbon block, 1 micron) filters the water coming out of the fresh tank or when running direct from city water,before it hits the faucets.

        1. Absolutely right about avoiding carbon-block filters at the inlet, Mark! We always use a sediment filter in line, but don’t want to block any chlorine that might be in the city water from entering the tank, as that helps keep it safe.

      2. The Camco inline filter you reference in this article is labeled as a “KDF/Carbon” filter and indicates that it reduces chlorine. Is that the inline filter that you use regularly? Or do you only use it when the quality of your water is unknown or you can only access well water? Thanks again, guys!

        1. Hi Mark! Thanks so much for catching that. The image of a carbon block filter was used in error, and we’ve replaced it with a photo of a more typical sediment filter housing. We only want to block chlorine when we’re using the city water directly, not when we’re filling the fresh tank, since any small level of chlorine that enters the tank from a city water connection helps keep the water safer while stored in the tank.

  9. In the Army, a water buffalo, which is a trailer with a water tank, had to be drained, rinsed and sanitized, same idea, bleach and water, weekly. Sitting outside, sometimes in the hot sun accelerated the need. In our RVs, the water tank is usually in a cooler area so it will go longer.

    I should’ve known better, but I hadn’t sanatized ours and we were on a trip. I smelled the water coming out and knew I shouldn’t brush my teeth with it or drink it. My poor wife didn’t notice, and ended up sick. I hugged my wife, kicked myself for knowing better, and it now gets sanitized before every camping season.

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