When set to the height of the main control valve from the float pilot valve to stop water supply intakes closed, when the water level drops, the main control valve from the float pilot valve opens to the pool water intake, automatic water level control precision, from pressure level disturbance; float valve diaphragm through the control can be installed anywhere with the height of the pool and use of space, maintenance, testing, inspection convenient, reliable sealing and long service life. Diaphragm valves reliable performance, high strength, smooth action applies to pipe diameter less than 450.