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.
When the float valve is used on a cold water storage tank where there is no possibility of hot water entering the tank a suitably sized plastic ball float and be attached to the end of the float valve. Where there is the possibility of hot water entering the tank such as a header tank connected to an open vented cylinder a copper ball float must be used.