Float valves are designed to fill water storage tanks. A float is connected to the long arm which is in turn connected to the valve body which either rises or falls depending on whether the tank is emptying or filling. When the tank empties, the float falls and the arm which is connected to a washered “Piston” retracts from the “Seat” of the valve causing the water to gush in. Conversely when the float rises; the piston slowly closes against the seat and shuts off the water supply. They are very economical and easy to fit and can avoid having to change or replace an existing brass float valve.