On our Beaver, there was a solenoid valve under the bottom drawer in the kitchen that turned the water on and off when filling the fresh water tank. It was a plain old ASCO industrial solenoid. If you hooked up to a water supply and got a grain of sand or rust particle lodged in the valve, this could prevent it from closing. When you dissemble the valve, just be sure to totally dissemble and check the little needle on the top of the solenoid shaft that moves up and down. It's not uncommon for this needle to get obstructed by a particle.
We always fill our tank, turn off the city water and use the coach pump, even when in a campground for a stay.
Monaco 2004 Signature 45' Castle IV Detroit 60
Towing 2015 Jeep Grand Cherokee diesel