1" Watts 800M4 Anti-Siphon Pressure Vacuum Breakers prevent the reverse flow of polluted water from entering into the potable water supply due to backsiphonage. Most commonly found, but not limited to, lawn irrigation systems, the pressure vacuum breaker is usually located outdoors. Bottom inlet, side outlet. Fully testable. Full port, quarter turn ball valves on inlet and outlet. Constructed of high quality bronze.