Originally Posted by Eggbeater
Thanks, the leak is definitely not being caused by the closed on board system.
The leak only happens when using city(shore) water. When I shut off the water supply the leak stops. I thought it may have been coming from the water heater, but I have not been able to confirm or dismiss the heater as the source when on the city water to the RV.
As suggested by 'Stevegd007' the on-board pump internal check valve could be leaking allowing city water to backflow thru pump filling/then overflowing the fresh water tank
City water and pump supply same plumbing system so pump has the internal check valve to stop backflow when using city water
Remove pump suction line..turn on city water and see if water flows back thru pump. If so replace pump check valve, install an in-line check valve on pump suction line OR run pump and possibly clear any thing holding check valve open
One other source could be 'FILL Valve' if you have one that you turn to fill fresh water tank or turn to use city water ....o-rings go bad and fill valve leaks----filling/overflowing fresh water tank
SO.....is your fresh water tank FULL and OVERFLOWING???