My fresh water by pass hook up that is supposed to by pass the fresh water holding tank is now filling it up. Does anyone know what could cause this problem?
Is the check valve located in the pressure relief valve?
Not familiar with your system but the check valve should be between the fresh water tank and where the dock hose fitting is plumbed into the cold line. I have seen the check valve built into this tee for the dock hose fitting.
I assume that the inlet from the shorewater connection T's into the water supply line just AFTER the pressure pump. The inlet to the pressure pump should have an inline filter. The outlet to the pressure pump should have a check valve. If there isn't one there, then install one.