Valve that prevents the flow of water behind it if the inlet pressure drops below the value set on the pilote valve. Used, for example to secure the propper pressure in the fire protection pipeline by cutting off domestic water in case of fire. Body: ductile cast iron GJS-400 (flanged valves), gray cast iron GJL-250 (threaded valves), membrane: NBR nylon reinforced (flanged valve), EPDM nylon reinforced (threaded valve).