Watts 1″ relief valve 0274934 this boiler pressure relief valve is used in hot water heating and domestic supply boiler applications to protect against excessive pressures on all types of hot water heating supply boiler equipment. It consists of a bronze body construction with npt threaded female inlet and npt threaded female outlet (drain) connections, non-metallic disc-to-metal seating, stainless steel spring, and test lever. It resists corrosive water conditions, sticking and freezing, and prevents water and sediment from being trapped in the seat. It is designed for emergency safety relief, not as an operating control. The pressure setting is 30 psi (206.9 kpa).