The 1-1/2 in. Model 975XL3BFSS Reduced Pressure Principle Backflow Assembly is ideal for use where Lead Free* valves are required. Designed for installation on potable water lines to protect against both backsiphonage and backpressure of polluted water into the potable water supply. Assembly shall provide protection where a potential health hazard exists. Features slow closing resilient seated UL/FM approved butterfly shutoffs with supervisory switch. For indoor or outdoor use.