Series 9D Dual Check Valves with Intermediate Atmospheric Vent prevent the reverse flow of hot or cold polluted water from entering into the potable water supply. It consists of a brass body with stainless steel internal parts, integral strainer, and two durable, tight-sealing, rubber check valves. Series 9D is designed for continuous pressure, non-health hazard applications in smaller supply lines, such as laboratory equipment, processing tanks, sterilizers, dairy equipment, and specifically for boiler feed lines. Minimum Working Pressure: 25psi (172kPa), Maximum Working Pressure: 175psi (12.06 bar)