Thursday, December 8, 2022


Water pumps out of RV’s city water inlet



Dear Gary,
gary-736I keep my 29-foot Dutchmen Class C parked under my pole barn.  It’s plugged in for power but nothing else is hooked up. I’ve just noticed that when I turn on the water pump, it pumps gallons of fresh water out through the park water hose inlet. It’s emptying my fresh water tank. When I turn the pump off, it stops. The pump is only a few years old. I would appreciate any guidance. Thanks! —Jim

Dear Jim,
All RVs have at least two backflow preventers (check valves) in the fresh water plumbing system. Some RVs have three and some actually have four backflow preventers. Every RV has one at the city water inlet which allows water to flow from the campground into the RV. The backflow preventer at the city water inlet has obviously failed in the open position. It will have to be replaced, or at least a new one installed right behind the existing one.

check valve RV Doctor 764Since it failed in the open position, it’s not really necessary to remove it (though it’s advisable if you can). A new backflow preventer can simply be installed just inboard (downstream) of the old one. That will prohibit water pushed by the onboard pump to be forced out the city water inlet. Actually, it’s not a difficult task for the average handyman to accomplish in a few minutes … once you gain access to the rear of the existing check valve.


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6 years ago

This also happened to me. To fix it, I pushed the back flow preventer in with my finger while the water was flowing out and then it worked correctly after that. Try this first before replacing the backflow preventer.

6 years ago

I had an experience where I placed one of those screen washers in the end of the hose with the screen bulge going into the backflow preventer. The screen made contact and prevented the backflow preventer from working.