Ugh… it was awful.  As we started to lean into an RVing lifestyle, we rented a variety of RVs to find which style fits our style.  We learned on our first trip with a rental that using water from an onboard system could be unpleasant.  Memorably unpleasant.

From the beginning, we were hesitant to use the on-board water because we did not have complete control over what went into the fresh water tank.  We did not want to rely on misplaced trust in any number of people that we did not know renting the RV and being conscientious in filling the fresh water tank cleanly.  We went into our first rental experience expecting bad water and reality met our expectations.

The water smelled bad, so we did not attempt to use it for cooking or brewing our morning coffee.  We compensated for the unusable water supply by carrying several gallon jugs and cases of bottled water with us. We would be okay with carrying extra water on short trips, but it was not going to be sustainable with the amount of travel we envisioned for ourselves.

Once we decided on the type of RV that was best for us and took delivery of our first Airstream, my understanding of the water system and its maintenance requirements expanded a bit. Along with the convenience that we could build into our trips by sanitizing the fresh water system, I learned about the things that could make sanitizing a must-do.

Do I need to sanitize my RV’s water system?

Yeah, you do. 

Sanitizing our fresh water tanks is necessary because it mitigates issues that can develop with algae, bacteria, mold, and other contaminants.

• Algae can cause a foul taste and odor.  It can also cause the water to appear murky.  Foul tasting, murky water isn’t appealing for use in cooking, drinking, or daily hygiene.
• Bacteria such as E. coli, salmonella, or coliform bacteria could cause gastrointestinal issues such as abdominal discomfort, diarrhea, and nausea/vomiting.
• Mold needs moisture and darkness to grow and that is exactly the environment we have with our fresh water system.  Mold could be the reason behind a musty or earthy taste and individuals sensitive to mold may experience a reaction to mold-contaminated water.

Maintaining our on-board water systems is not too difficult, but it isn’t always front of mind for some of us and because sanitizing the water system can eat up an afternoon or more, it may be tempting to delay the routine chore or to omit the maintenance completely. 

How often should you sanitize your RV water system?

Manufacturers recommend sanitizing before storage or after storing for a period of time, but no one defines what “period of time” means. Sanitizing fresh water tanks every six months is common.

Consider triggers other than time by sanitizing fresh water systems:

1. When we want to proactively prevent growth, or suspect that algae, bacteria, or mold is in our water supply.
2. After contaminates are introduced during routine maintenance.
3. When we don’t want to use limited storage space for bottled water.
4. When well water is used to fill the freshwater tank because it is different than water sourced from a treated, municipal supply.
5. When we want to feel confident that we have a clean, safe waters supply for hygiene, to cook, and to water our pets.

RVs often sit in storage for weeks or months at a time and the dark, humid environment within a freshwater system is ideal for mold, algae, and bacteria growth. While traveling, we may refill our tanks from treated, municipal sources with water quality that is different from standards we are accustomed to.

Also, water levels decline as we use up the supply providing more air to the system and more opportunity for growth.

Contaminates can enter the RV’s system through routine maintenance or by simply removing the cap to the fresh water intake. The hose we use to fill our tanks may be dirty on the inside or already contaminated and we may move those contaminates into our tanks. Also, all hoses are not the same.

Ensure that the hose used to fill fresh water tanks is designed for drinking water, like this one.

Filters are the first step in protecting our fresh water supply. I wrote an article on the four types of filters commonly used by RVers that you can see here.

Erring on the side of caution, I sanitized more often than was probably required at first.  I wanted to ensure that we had a clean water supply and would sanitize when none of the other triggers were present.

Sanitizing our tanks was triggered by events such pulling the Airstream out for a trip after a few weeks of storage or detecting an off-putting odor or taste after filling our tank at an unfamiliar park.

Other events that can trigger a sanitation effort for us include:

1. Going into storage or after sitting in storage for several weeks.
2. Preparing for a long trip.
3. Detecting an off-putting odor or taste.
4. Adding new components to the system.
5. Suspecting that the system was subjected to outside contamination.
6. Regular preventative maintenance schedule.

As we got more experience, we got more comfortable with a less-frequent sanitizing schedule.

How much bleach do you use to sanitize a freshwater tank?

Bleach contains sodium hypochlorite (NaClO) as the active ingredient. When bleach is added to the water in our tanks, the sodium hypochlorite dissociates into sodium ions (Na+) and hypochlorite ions (ClO-). The hypochlorite ions provide the disinfecting and bleaching properties, and it only takes a little bleach to create a sodium hypochlorite solution strong enough to sanitize our fresh water systems. How much bleach is enough?

I looked at user manuals for several manufacturers and a dozen models and found that the formula was the same for each one.

Multiply the fresh water tank capacity by 0.13 to get the number of ounces of bleach required to sanitize the system. The formula works out to 1/4 cup of non-scented, liquid (non-scented) household bleach for every 15 gallons of stored water.

9 Steps to Sanitize

Sanitizing a fresh water system takes just a little effort but can take several hours because we must give the sodium hypochlorite solution time to do the work.

Here are the steps to sanitize an RV’s fresh water system.

1. Turn off the water heater and let it cool.
2. Drain the system by opening valves in the water heater and fresh water tank.
   • We cannot drain our fresh water tank completely by opening the drain valves underneath the RV, so we also turn on our water pump and run water through the faucets to ensure we drain as much as possible.
3. Add 1/4 cup of bleach for every 15 gallons and refill the system with potable water.
   • To introduce the bleach into our system, we hook up the supply side of our water hose to a potable water source or to the discharge end to our RV, whichever is lowest. Then, we use a funnel to pour the required amount of bleach directly into the other end of the hose. Being careful not to spill the bleach, we make the final connection, turn on the water, and fill our tank.
4. Pump the solution through the system
   • Once the tank is filled, we turn on the water pump and open each faucet one at a time until we smell the chlorinated water.
5. Let it sit for 4-12 hours
   • As a rule, the sodium hypochlorite solution should sit for between 4-12 hours. Some manufacturers suggest driving the RV around a bit to splash the solution into areas not otherwise contacted by the sanitizer. Also, the owner’s manual for our Airstream suggested that doubling the amount of bleach would lower the required contact time to one hour.
6. Drain the fresh water system again
7. Refill the system with potable water
8. Open the faucets and shower one at at time to flush the chlorinated water from the system
9. Test for chlorine odor or taste. If present, rinse and repeat

Wrapping up

Using water from an RV faucet is not equal to opening a faucet in the house because there is a dirty bridge between the municipal water source used to fill our freshwater tanks and our RV’s faucets. The “dirty bridge” includes the campground faucet, our hoses, filters, connections, and freshwater tank.  So, we need to sanitize our water systems.

Sanitizing the fresh water tank in an RV is a crucial step in maintaining a clean and safe water supply while traveling. Neglecting this simple maintenance item can lead to the growth of harmful bacteria and pathogens which could jeopardize our health and give us stories we’d prefer not to tell.

I hope that this article answered your questions about whether sanitizing our fresh water system is necessary, how often to do it, and gave you the specific steps to take. Good luck with your sanitizing efforts and we hope to see you down the road!

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