That was another one of the problems on our returned coach. I was informed my valve was installed too low which would have caused a siphon. Mine was leaking with only a 1/3 of a tank of water and no fresh water hose connected pressurizing the system.
Chuck in SW FL
Digital 2021 Cornerstone "B"
A "Digital" 2019 Cornerstone "B" Traded
A "Classic" 2014 Anthem 42 RBQ---Sold