Fresh Water Storage: Is It OK To Leave Water in RV Tank?

Updated on

While water is a necessity, it often feels like a luxury in an RV, particularly if you have running water from a tank. You have the bonus of boiling a kettle, washing dishes, rinsing vegetables, and taking a shower, all from the comfort of your RV. Having water is especially important if you enjoy boondocking over staying at campgrounds. So, how long to keep fresh water in RV tank?

Depending on the quality of water you put into your fresh water tank affects storage time. If the source is treated city water, the recommended time is 3 – 5 days for drinking and 10 – 14 days for washing and bathing. Using untreated water or from a natural source could shorten the timescale. If you do not use your RV regularly, using and changing the water frequently, you should empty the tank after every trip.

sanitize rv fresh water tank

This article will discuss the importance of changing fresh water, recognizing and knowing how to deal with contamination, and the best way to maintain a fresh water tank.

Can You Store Water in a Freshwater Tank Forever?

If you regularly use your RV and frequently empty and refill the fresh water tank, you should not have any problems. However, if the water sits unused, it can become unsafe to drink. There appears to be no definitive timeline, as it depends on your water source, water usage, and RV water system. 

In the western world, we rely on chlorine to protect our drinking water. We depend on the city water connection from our home taps to be safe, which is tightly regulated by the authorities. However, when we introduce a water system outside the city’s testing and monitoring systems, we must ensure the drinking water is safe.

By introducing storing water in a tank, we have introduced a few elements that affect the quality of our drinking water. Chlorine is a volatile substance that decays under certain conditions.

Chlorine evaporates when exposed to air. Depending on the chlorine level in your tap water, it takes approximately 110 hours (4 ½ days) for the chlorine to completely evaporate from 10 gallons of water. It leaves the water vulnerable to bacteria.

Many variables can affect the speed chlorine evaporates from water in your RV.

  • Ambient temperature
  • Amount of chlorine present in the water supply
  • The surface area of the holding tank
  • Whether UV light can penetrate the RV tanks

Causes of Water Contamination Inside an RV Freshwater Tank

There are several causes of water contamination inside an RV fresh water tank, and we are not always confident if the water source is trustworthy. We might think we are filling up with a reliable source when we are not.

Unknown Water Source

In 2017 at the Little Wood River Reservoir campground in Cary, Idaho, campers inadvertently drank water contaminated by coliform bacteria. A type of bacteria present in the feces of animals and humans. Some forms of coliform bacteria can cause health problems, making people unwell. The water source, a well, was closed for further investigation.

Idle Water

When water is left idle in water systems, it can provide the ideal breeding ground for Legionella bacteria to grow. The shift in water temperature can cause the bacteria to multiply. During a shutdown period, disinfectants or biocides, such as chlorine, normally inhibit Legionella growth. 

If the contaminated water is aerosolized, for example, by a shower or faucet, the Legionella bacteria can be inhaled, creating the risk of developing Legionnaires Disease or lung disease.

Dirty Freshwater System and Tank

If the water system and tank have been left empty for a while, a small amount of moisture remaining in the tank can cause bacteria growth. Outside temperature can affect the speed of development, the warmer and more humid the climate, the faster bacteria growth. Therefore, sanitizing your RV’s fresh water system and the fresh water tank is crucial before using.

How Long To Keep Fresh water in RV Tank


A general rule is that keeping fresh water in an RV water tank for up to three days should be okay. After this period, there is the risk of too much bacteria growth, compromising the fresh water system and water safety.

For Washing and Bathing

As soon as water sits in your tank without being used and refilled, it can be unsafe for drinking. A general rule of thought is two weeks for washing and bathing. It might seem okay to use the water for these purposes. However, if you ingest idle water, there is the risk of Legionnaires disease and other bacterial contamination. 

If clean and safe water goes into your RV fresh water tank, but the tank is dirty, the water quickly becomes contaminated.

Is It Safe To Bathe in Water With Molds?

The recommendation is not to swim in a pool with mold or algae. The same applies to bathing in moldy water. Bacteria can pose health risks if you bathe in water with molds, causing skin, ear, and eye irritations.

Signs of mold indicate that your RV water system is not adequately maintained, and chemical imbalances are causing bacterial growth.

Check Out How Long Can You Keep Fresh Water In The RV Tank Before It Turns?:

Signs That Water From Freshwater RV Tank Is No Longer Fresh

Even though there is a suggested two-week timescale before the water goes foul, if you notice any of the following signs, it could indicate that the water in your freshwater RV tank has spoiled.

Unpleasant odor. Sometimes the water from your RV fresh water tank can smell plasticky. It does not mean the water has gone stale. It can occasionally pick up the smell of the plastic tank, mainly if the temperature is warm. However, if you have foul-smelling water with a strong, unpleasant odor, it could suggest it is no longer fresh.

Unpleasant taste. Besides the chlorine taste associated with tap water and a hint of plastic from your tank, foul-tasting water is another sign of impure water.

Change in watercolor. Discoloration of water, such as orange, brown, or green tinge, can signal water contamination.

Water lines clogging. If your RV water system begins jamming, it is another sign that your water is polluted.

Feeling unwell and nauseous. Suppose you start to suffer from stomach cramps, diarrhea, nausea, and generally feeling unwell. If this happens, it is a good idea to consider sanitizing your RV’s fresh water tank and system, especially if the water has been left unused for a while. 

If you suspect contamination is affecting your RV water at any time, you can test for impurities.

How To Drain RV Fresh Water Tank

It is easy to drain an RV’s fresh water tank. There are a few steps to follow.

Turn off the water heater, and wait for the water in the heater and the freshwater system to cool down.

Turn off your RV’s water pump and open all the faucets, such as sink faucets, shower, and outside shower.

Bypass the water heater to prevent water from entering.

Locate the drain valve underneath the RV and open it, releasing its fresh water tank contents. Open the tap slowly to prevent splashing and creating a mess. You should plan your emptying location, as depending on how full your tank is, you could dump a lot of water.

Open the red and blue low-point drains for hot and cold water. 

Switch back on the water pump. It will help to empty any remaining water in the water lines. Once the water has stopped running, turn off the pump to prevent damage.

Sanitizing a Freshwater Tank

As part of the routine maintenance of an RV freshwater tank, in addition to emptying regularly, the freshwater tank should be sanitized. It only takes a small amount of moisture to encourage the growth of bacteria. Even if you use a water filter, your tank needs sanitizing.

Depending on how often you use your RV and the freshwater system will affect how regularly you sanitize. If you full-time in your RV, sanitizing once a year might be sufficient. However, if you are an infrequent RVer, you might find it safer to sanitize before each trip.

You can buy specific RV products to sanitize your fresh water tank or use bleach in a recommended dilution.

Before sanitizing your tank, check the faucets are closed.

Calculate how much bleach solution you will need to sanitize your tank. A rough guide is ¼ cup of bleach for every 15 gallons of water your RV tank requires. Household bleach is acceptable to use.

Pour the bleach mixture into your tank using a sanitized funnel and jug.

Once the tank is full, turn on the pump and fill the water heater first. Then open the faucets, one at a time, running the water through the taps until you smell bleach at each faucet. This cleans the water lines.

Then close the faucets, and leave the bleached water to stand for 12 hours.

Drain the system entirely, and fill it with fresh, clean water until the water running through the faucets is bleach free. You might have to repeat this part of the procedure a few times.

Proper White Filling Hose

The correct hose for drinking water is a white filling hose rated safe for drinking water use. It is manufactured following FDA guidelines, using approved materials that are non-toxic.

Use of Water Filter

Having safe, clean potable water makes RV adventures so much easier. However, deciding on your water filter system can range from simple to complex. You might only use city water and be okay. Or, you could fill up with water from a faucet next to the black waste or use a suspicious-looking one at a truck stop. 

Some campgrounds use natural water sources, and if you travel outside the US, you might be unsure of the water quality. If the water does not run clear, you will likely need a backup system to improve the purity of the water.

An RV water tank filter is similar to a house water filtration system. It can improve taste and odors. They remove sediment that could block your system. More advanced systems, such as UV treatment lamps, can remove unwanted bacteria and contaminants and make it possible to use water from streams. Different sizes and types do various tasks. 

In addition, they are more environmentally friendly, as they eliminate purchasing plastic water bottles as your onboard fresh water system is safe to drink.

How To Deal With Algae In A Fresh Water Tank

Algae growing in your freshwater tank will cause significant problems in the tank and throughout the freshwater system. The algae are unsightly and block faucets, pumps, drains, and pipes. The presence of algae is also a significant health risk.

UV rays from sunlight and heat accelerate algae growth in the water tank. However, many RV freshwater tanks are colored or inside the RV, meaning they are not exposed to UV light, therefore limiting algae growth.

As with most problems, prevention is always better than cure. So be sure to drain all freshwater systems from the RV and water tank when not in use and adopt a robust cleaning routine for your RV’s water system, ensuring algae is never an issue. Never leave water in the RV tank.

However, if algae are present in the freshwater tank, follow these simple steps:

Firstly remove the water tank drain plug if fitted or use the low point drain, allowing water to escape along with as much algae as possible. This will help prevent the algae from blocking other fresh water system parts.

If fitted and accessible, remove the access lid of the RV’s fresh water tank. With a soft-bristled brush and plenty of fresh water, reach into the RV freshwater tank, clean the inside of any surface mold, and drain all residue.

Replace the drain plug and shut all drain faucets.

Remove all filters from the end of the faucets and clean them. Replace on completion of the final step

Remove and clean the potable water pump pre-filter. Replace.

Using a ratio of ¼ of a cup of bleach to 15 gallons of water, work out the capacity of your tank and add the desired amount of bleach to a gallon of water, then add the diluted bleach to your tank.

Fill the tank with fresh water and let the solution sit for 12hrs. The bleach will help break down and kill the algae and other bacteria in the tank.

Drain the tank again, refill mixing bleach and water in the same ratio, and proceed with a standard tank and water system sterilization.

On completion, replace the inline water filter if fitted.

The grey and black tank can be cleaned the same way as the fresh tank, using a standard sterilization procedure. Any other storage tank should also be cleaned in the same way, whether it is a fresh water storage tank or holding tanks of any description.

Check Out 3 Ways to Eliminate Algae Growth in Water Tanks [Guaranteed]:

Related Questions

Is It OK To Leave Water in RV Tank?

If you are using your RV often and regularly refilling your freshwater tank, you should be okay to leave your water in your RV tank. However, if you infrequently use your RV and intend to drink your water, it should be left in your tank for three days maximum. Chlorine evaporates, leaving your water unprotected from bacterial contamination.

How To Refill Fresh Water Tank During Camping

An RV’s fresh water tank can hold anything between 20 and 100 gallons. At some point, you will need to fill up with water. How often will depend on how frugally you use the water and how many people are onboard. It is simple to refill, and the most accessible place to fill up is at a water hook-up point.

Use a suitable hose. A white filling hose is an approved FDA hose. Use the hose only for filling the RV’s fresh water tank to keep it hygienic.
Pull up close enough to the water spigot, so your hose can reach it.
Connect one end of the hose to the faucet, ensuring it is securely on to avoid leaks.
Screw the other end of the hose to your RV’s water intake. 
Once connected at both ends, slowly open the faucet. You can feel and hear the water flow into your tank. Regularly check the water gauge level to let you know when the tank is full.

How Long Should RV Water Hose Be?

Most RVers carry a 25-foot hose as a minimum. Some people find this adequate, while others prefer a secondary hose of 25 feet that can couple together. Another combination is to take one 25-foot hose and one 50-foot hose. The combination of hoses you find suitable for your situation depends on the weight and storage space available in your RV.

How Long Can You Leave Black Water in RV?

You should dump an RV’s black water when it is ⅔ to ¾ full. How frequently it depends on how many people use the RV toilet and whether liquid, solids, and toilet paper are going into the tank. Regular emptying prevents smells and clogging of the black water system.

How Much Is the Cost To Replace RV Fresh Water Tank?

Several factors affect the cost of replacing an RV’s freshwater tank:

– Size
– Tank material
– DIY or professional fit
– Ease of accessibility to fit the tank
– A rough estimate is $100 to $30

A rough estimate is $100 to $300 for the tank purchase. The installation price can be up to $1,000 if being professionally installed.

Bottom Line

How long to keep fresh water in RV tank depends on several factors. If your RV is in regular use or you are full timing in your RV. You are likely to be emptying and filling your fresh water tank regularly enough and do not have to consider draining the tank. You should sanitize it once a year to keep fresh. Again, that is dependent on the water supply. If it is reliable water, once a year should be plenty. However, you should clean freshwater tank more often if refilling from a natural, suspicious, or dirty source.

If you occasionally use your RV, you should empty your tank every three days. The reason for emptying as often as three days is because the chlorine that keeps the water safe begins to evaporate, leaving the water vulnerable to impurities such as bacteria and Legionnaires disease.

Here are a few signs to look for to recognize if your water is no longer fresh.

  • Unpleasant smell
  • Bad taste
  • Discoloration
  • Water lines begin to clog
  • Feel unwell

If you are using your water for washing and bathing, a general rule is that it is okay to leave the water in the tank longer, up to two weeks, providing you do not ingest the water.

Having a regular maintenance routine for your RV’s water system and tanks is vital to keep them sanitized and your water safe.

Photo of author
Written by William Perry
William was born and raised in the United States and currently lives in Utah. A retired police officer, he is the father of three and grandfather of six. Along with writing, he enjoys traveling, the outdoors, reading and spending time with his grandchildren.
Search This Site