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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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Ditch the bottled water! Major cities sanitize their drinking water using ultraviolet light, and now you can, too. Acuva’s UV-LED system makes water safe to drink, using a fraction of the space...Show More

Ditch the bottled water! Major cities sanitize their drinking water using ultraviolet light, and now you can, too. Acuva’s UV-LED system makes water safe to drink, using a fraction of the space and power… perfect for RVs.

Check out our Acuva installation video here

Get 10% off any Acuva system when shopping online at Acuva's website and using the discount code listed here.

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Sometimes we receive products for evaluation at no cost and may use affiliate links to the products and services from which we earn commissions. For example, as an Amazon Associate, we earn from qualifying purchases. That said, it's important to us to let you know that our opinions are our own. We only recommend products we believe deliver real value and that we can confidently recommend without reservation. You also won’t pay an extra penny by using our links. Thanks so much for supporting RVgeeks as we work to create helpful RVing-related content that we hope enhances your RVing life!

Even though we're handy RVers, we're not professional technicians. So although we're happy with the techniques and products we use, you should be sure to confirm that all methods and materials are compatible with your equipment and abilities. Regardless of what we recommend, consult a professional if you're unsure about working on your RV. Any task you perform or product you purchase based on any information we provide is strictly at your own risk.

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