We are talking apples and oranges.
To open the valve for filling my water tank I have a square lighted switch that says tank fill. It is mounted along with other switches of the same design that are for gray water bypass, macerator, port dump, water pump, prime, etc. Pushing the switch for filling the tank once opens the valve and a light adjacent to the switch lights to indicate the valve is open. Pushing it again closes the valve and the light goes out.
I think the switch you are talking about is a toggle switch on the tank level annunciator panel.