My city water/fresh water fill valve is a Swan Quick Fill with a two positon lever. I too had my fresh water tank filling up when the Swan valve was in the city water position. I have a manual shut off valve between my water pump inlet and the fresh water tank. To eliminate the water pump check valve, I closed the manual valve and the fresh water tank was still filling. In fact, I could hear the water trickling into the tank with the Swan valve against the stop in the city water position. I took the handle off the valve and with a cresent wrench, moved the valve further than the handle would allow. Sure enough, the water stopped flowing. It would seem the internal ball valve is just slightly off so that with the handle installed, it doesn't fully move to the city water position. It doesn't look like you can open the valve up to replace any internal parts and a new valve is $139! Guess I'll just keep using the cresent wrench for the time being.