Water lines

[CORNFED__5-0_]

I have a 2008 Forest River (Cardinal) 5th wheel that I bought new. I hand never had any issues with the water lines, until now. When I am hooked up to shore water it is some how crossing over and filling my fresh water storage tank. It is over flowing out the vent line.

Now I know that the on bored water and shore water lines inter mis some how and have chased them every ware I can and have checked all the faucets for issues but I find nothing.

I found one small leak near my on board filter but nothing else.

I did notice that when I am using shore water and the pump is off the filter is empty. And if shore water is on the system is pressurized and the electric water pump will not turn on.

I have a pressure regulator in line from the shore water restricting the water flow to 45 to 50 psi.

Any ideas on what the issue may be and how to correct would be helpful.

[CORNFED__5-0_]

Thank you to everybody. Used all the advice checked all the valves and it appears to have corrected its self. I turned off shore water and had my daughter take a shower using the pump. I guess that was it. Thanks again.

[Old-Biscuit]

Do you have a gravity fill for fresh water tank OR vlaves/switches you change on a water panel?

If you have water panel......fresh water tank 'Fill' valve could be leaking thru.

OR (most likely) the on-board water pump internal check valve is leaking allowing water to back flow into fresh water tank.

Running pump sometimes will clear scale/debris on check valve allowing it to fully close.
Check valve can be replaced in pump.....about $15
Install an in-line check valve on pump suction line.....about $10
Replace pump....upgrade about $70

[beemerphile1]

Assuming that you have the fill valve in the correct position - the check valve at the water pump is allowing reverse flow.

Simply using the water pump briefly may remove the object blocking the check valve from sealing.

[owenssailor]

There is a check valve in the pump. It is likely passing. I had this happen. Solution - new pump

[Bob_Olallawa]

Check the valve positions, sounds like the city water to tank fill valve is in wrong position.