Watts T062020 0062020 3/4" 007 Series Bronze Double Check Valve Backflow Preventer with QT Shutoff - This 3/4" double check valve assembly backflow preventer helps prevent the backflow 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 non-health hazards and for contaminants at the service line entrance.