This 1 1/2 IN anti-siphon pressure vacuum breaker, series 800M4QT, prevents the reverse flow of polluted water from entering into the potable water supply due to backsiphonage. It is ideal in health hazard continuous pressure applications such as irrigation systems and industrial process water systems where the water enters the equipment at or below its flood rim. It consists of bronze body construction, silicone rubber check valve disc, plastic check valve seat, stainless steel springs, a bonnet with silicone rubber O-ring seal, a lightweight plastic disc float, lever handle shutoffs, and test cocks for winterization draining. Maximum pressure is 150 PSI (10.3 BAR). Minimum pressure is 15 PSI (55kPa).