How long is it safe to leave fresh water in the tank and system between trips?


Staff member
I've often wondered how long it is safe to let fresh water sit in the tank and system between trips. We almost always fill with city water that is treated. How long can treated water sit in the tank and system before biologics will start growing or will they?

The longest we have left fresh water sit in the tank and lines between uses is a couple months. The next time we get the trailer out for a trip, we always flush the fresh water tank, then fill it with treated city water. Then we flush the kitchen sink lines by letting the faucet run for a couple minutes. We have our Clearsource dual filter permanently mounted in the basement and always remove the filters so they can dry between trips.

Doing this routine we have never had any smell, taste, or bad effects from leaving water in the system.

What is your time limit for letting fresh water sit in your system?
More than a month, and i re-chlorinate. I don't know if a rule of thumb for this. Sometimes i leave the chlorine water in the fresh water tank, and sent it back through the lines, as long as i smell chlorine in the water coming out of the tap.
How much chlorine do you use?

Which leads to another question, is it better to have the tanks drained and dry vs. leaving water with chlorine added in the tank?
For a 24 hr or longer treatment, I use 1/4 cup per 15 gallons.

For a quick sanitize double it. 1/2 cup per 15 gallons.

Dry vs wet? No data but I worry that with the large volume of air and minimal chorinated water after draining, that the chlorine would gas out and leave dampness that could mold.