FEBCO 2613 1" 850 Double Check Valve Backflow Preventer Assembly with Union Ball Shut-Off Valve. This 1 inch small diameter double check valve backflow preventer assembly is designed to prevent the backflow of polluted water from entering into the potable water supply due to back siphonage 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 non-health hazards and for contaminants at the service line entrance. This assembly consists of a bronze body construction, union end connections, quarter turn ball valve shutoffs, top mounted test cocks, two in-line independent positive seating check modules, captured springs, and replaceable check discs and seats.