Had a similar problem with my valve, but it was stuck open (piece of trash or crud) allowing the tank to fill overnight & water everywhere underneath the RV. Panic!! Until I realized it was coming out the overflow tube. So I have managed to get the valve clean for now, running pump & park water. Monitoring the water level in my tank just to make sure it holds. Will get a few replacement parts & fittings for future plumbing nightmares!!
Ralph 2005 Alpine 40FDQS
2005 Alpine 40 FDQS, 2011 Chevy Equniox, Ready Brute Elite Towbar, Ralph & Debbie with Sassie & Shelby