water system not holding pressure

Typically 2 check valves in RV plumbing system
One inside city water inlet....stops water from leaking back out when using ump
One internal of pump.......stops water from backflowing thru pump when using city water connection

With a water panel and a valve used to fill fresh water tank via city water connection........valve is all that is used to stop flow thru fill valve to tank.


So if water is leaking out of city water connection when using pump....that check valve is bad

If fresh water tank is 'filling' when using city water connection.......fill valve is leaking thru OR pump internal check valve is bad.

You can install an in-line check valve in pump suction to isolate pump (without rebuilding/replacing pump). Then if tank still is getting water..then fill valve is leaking thru.

Shurflo in-line check valve


Here is a basic RV water system.....this one has gravity fill for fresh water tank but idea is the same

you need to replace your city water hook up valve
Yes it has a build in check valve.
remove the screen and see if it push easy or broken

Usually the inlet fixture has a check valve built in.