Watts 0391002 1/2" Reduced Pressure Zone Backflow Preventer Assembly is designed to prevent the flow of polluted water from entering into the potable water supply due to backsiphonage and or backpressure in accordance with national plumbing codes and water authority requirements. Its compact modular design facilitates easy maintenance with a single access cover for in-line repairs. It is ideal for protection in continuous pressure piping applications and at cross-connections identified as health hazards and for contaminants at the service line entrance. This assembly consists of a lead free bronze body, NPT end connections, quarter turn ball valve shutoffs with tee handles, top mounted test cocks, two in-line independent check valves, captured springs, and replaceable check seats with an internal relief valve for reduced space requirements.