City water filling fresh tank

Farmboy666 wrote:
I don't have a gravity fill, I have a city water connection, If I want to fill my tank I open the valve on the line going into my tank. When the tank is full I shut the city water off and turn the pump on. If I want to use city water the valve to tank is closed so if check valve in pump were to fail the water still can't get into the tank because the Valve is closed.

I understand what you do to use it but I think you’re making assumptions about how it’s plumbed. Since you didn’t really answer where the valve physically is, I’ll explain with a generic response. Even with a direct fill valve from the city water to the tank, you probably still have another path back through the pump. The fill port to the tank is completely separate from where the pump draws its water from the tank so shutting that valve doesn’t do anything to help a broken pump check valve. Tank fill valves are simply a shunt to over to what would have been a gravity fill.

Search Google images for “rv water system diagram” and look at the 2nd picture. It shows a 2-way valve at the city inlet. There’s still a pressurized path that can fail back through the pump.

Maybe there’s some other way your rig is plumbed but I can’t imagine it without more valves involved than necessary.