Fresh Water Fill Won't Shut Off

Mystery of the full freshwater tank

We recently had an issue with the onboard freshwater. The tank was filling on its own. We were baffled because we had the fill valve turned off. 

Some background. Winnebago Class A's, at least the 2020 Intent, does not have an external fill for fresh water like others. When the hose is connected to shore water a valve in the "water cubby" is opened and the tank is filled that way. Like many, if not all other RVs a switch on a panel inside the RV turns the pump on and off when you use it.

On the pump itself is a one way check valve that only allows water from the freshwater tank to be distributed to the RV. If this check valve is held open with some kind of crud or is damaged, water from the shore water supply can leak back through the pump and into the fresh water supply tank.

This, as we found out, can also occur if the shore water supply pressure is too low. It won't have the pressure needed to completely seal the one way check valve. This turned out to be our issue.

The Issue

Sever months back I had purchased a pressure gauge which connects to the shore water before it goes into the coach and provides a readout of the pressure, nice. Many years ago I had purchased a similar device with no gauge. I was looking for a way to attach my water filter to the shore water without having to turn the entire filter, just the fitting. Well this little gadget was just the ticket. I could screw one end into the filter and the other would attach to the shore water with its swiveling head. Genius!

The Fix

As it turns out, the device I had attached to the filter was restricting water flow, as it should, but only letting 20 psi through. This was not enough to force the check valve shut and over night it would fill the tank. 

I removed the device and reconnected all the hoses and BOOM! (John Madden quote for all you football fans) it was fixed. We are very glad it turned out to be simple and free instead of expensive.

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