Fresh water tank filled on its own.

[cheatham09]

Went camping this weekend for the second outing with the new camper. Hooked everything up Friday evening and Saturday morning the water was running out the fresh water tank on the ground. I thought right away a valve must be stuck and back feeding into the tank. I shut off the city water and turned on the water pump and ran water for a little. Drained the fresh water tank and turned back on the city water and everything seamed to be working fine. Has anyone every had the same issue?

[VTX Al]

The check valve in the onboard 12V water pump is defective. If unit is under warranty, your dealer will probably replace the entire pump assembly.

...VTX-Al

[Herk7769]

Crud can find its way from the hot water tank (bits of anode and calcium) into the cold water lines due to pressure changes when taps are opened and closed.

Similarly, that crud can be pushed into the pump head when city water pressure is then used.

When this crud blocks the one way check valve inside the water pump, city water can force its way past the check valve and fill the fresh water tank.

You did exactly right by removing pressure from the system and turning on the water pump. Water flowing through the pump can sometimes clear the bit that is holding the check valve open.