Originally Posted by claywilson1981
New to RVing and just bought a used Wildwood Heritage Glen 5th wheel.
Not sure if this is normal but wouldn't think it is.I drained the fresh water tank before I ever hooked up the water to it. I noticed the next day after hooking hose to city water hookup that the fresh water tank is full. There is a tank fill hookup next to the city water hookup. Did I do something wrong? Wouldn't think the tank would fill unless I connected to that port.
Since you're new to this, it may not be obvious to you that the "check valve" everyone is writing about is really a one-way flow valve in the pipe. Water can flow one way, but not the other.
It's often constructed as a pipe fitting with a metal ball and spring. The ball and coil spring are coaxial with the pipe. When water pressure pushes against the ball, it compresses the spring and water can flow around it. When water pressure is from the other direction, through the spring, it pushes the ball against the pipe opening and no water flows through.
The RV plumbing system has two sources of pressure, the water pump and the city water connection. Each has a check valve. If either one is on, water would flow out the other if the check valves weren't present.
The check valve at the water pump on your RV is leaking. There are a couple of causes:
1) You've turned on the water pump AND city water. Don't do that. If you do, it puts pressure on the check valve from each side, counteracting the spring and reducing its effectiveness.
2) There's a tiny grain of sand stuck in the check valve. (All water has tiny particles in it, it seems.) Standard practice is to
--Turn off city water.
--Turn on pump.
--Run water in several on-off cycles to flush the particle out of the check valve.
--(Optional) Continue running water from the fresh water tank until it is empty. This serves to flush the valve further, and consumes the water in the tank.