prevents the water heater pressure relief valve from opening, saves energy and eliminates a potential safety hazard. It is commonly installed in a domestic hot water system that contains a backflow preventer, a check valve or a pressure reducing valve. Measures: 13.7 in. L x 10.6 in. W x 13.7 in. H with 4.8 Gal. tank size, 10 lbs. weight and 3/4 in. connection size (NPT).