0061952 - 1/2 In Bronze Dual Check Valve Backflow Preventer with Intermediate Atmospheric Vent1 2 In Bronze Dual Check Valve Backflow Preventer with Intermediate Atmospheric Vent, Union Solder End Connections This 1 2 inch dual check valve backflow preventer with intermediate atmospheric vent helps prevent the reverse flow of hot or cold polluted water from entering into the potable water supply. This valve is designed for continuous pressure non health hazard applications in smaller supply lines, such as laboratory equipment, processing