Sanitizing the Fresh Water system

Before using the fresh water tank for the first time in a new RV, and before the first outing of the year, it is recommended that you sanitize the fresh water system. It is a relatively simple process...

1. If you have any in-line water filters built-in to the water lines inside the RV, you will either want to remove them or, hopefully, they have a shut-off valve in the water line before entering the filter.
2. Turn off the water heater and let it cool.
3. Add up the capacity of your entire fresh water system…that includes the holding tank and the water heater. Multiply the result by 0.13 to determine the number of ounces of unscented bleach you will need. For example, say you have a 40 gallon holding tank and a 6 gallon hot water tank for a total of 46 gallons. Multiplied by 0.13 equals 5.98 ounces of bleach needed. (It’s okay to round up a bit, but not too much.)
4. Fill the fresh water holding tank to about 1/3 full.
5. Mix the bleach with water in a one gallon container and pour it into the fresh water holding tank. (This prevents straight bleach from contacting anything.)
6. Fill the fresh water holding tank completely
7. Turn on the on-board water pump. You do not want to be connected to the city water supply
8. Turn on one faucet at a time and let the water run until you can smell the bleach solution, then turn it off. Do this for each hot and cold water faucet. Don’t forget the outside shower and the toilet.
9. Turn off the water pump.
10. Top off the fresh water holding tank and let everything sit for at least 4 hours.
11. Drain the hot water tank and put the plug back in.
12. Drain the fresh water holding tank.
13. Fill and drain the fresh water holding tank at least twice to rinse out the bleach solution.
14. Fill the fresh water holding tank again, but don’t drain it this time.
15. Turn the water pump back on. This will cause the hot water tank to fill.
16. Turn on each faucet and let the water run for several minutes to completely flush out the bleach solution.

Obviously this is going to use up quite a bit of water!

The water that will run through the water lines inside the RV will end up in your gray water holding tank. If you are worried about the amount of water that may end up in your gray water tank, you may want to do this procedure at an RV park or somewhere with sewer hook-ups.

Also, since you will be filling and draining your fresh water tank at least 3 times, this would mean a lot of water will be going onto the ground, some of which will smell like bleach. You may want to rig up some sort of hose from the fresh water tank drain to the sewer hook-up.

If you're going to head for an RV park so you can use their hook-ups (like on your first trip out each spring), call ahead and ask where the campground's waste water goes, explaining why you are asking. If it goes into a city sewer system, you'll be okay. But if it goes into the campgrounds own septic system, this may not be a good thing for the campground. Too much bleach in a septic system can cause problems and may cause the system to shut down, leaving many of your fellow campers upset. If the waste water goes into a sewer system, do steps 1-10 at home before you leave. That way, as you travel, the water will be sloshing around just a bit in the holding tank, and you will probably be ready for step #11 (draining) when you arrive.

There are other ways you could do this at home, if you are connected to a city sewer system.
There are special end caps for the sewer drain on the RV that are designed to hook up to a regular water hose. Pick up an inexpensive water pump of some sort (Camping World has one for $35) so you can pump the water into the sewer system at your house. You'll have to get a little creative here with the hoses, pump and fittings, but it should not be too much of a problem.


So, what do you do if you found this information too late and have used too much bleach? The information I have found suggests using either 1 quart of white vinegar or 1/2 cup of baking soad for every 15 gallons of water capacity. Use the same process as above for mixing the solution, getting into your fresh water tank and pumping it through the system.