Watts 0061888 3/4″ dual check valve this 3/4 inch dual check valve with atmospheric vent prevents the reverse flow of hot or cold polluted water from entering into the potable water supply. This valve 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. It consists of a brass body with stainless steel internal parts, integral strainer, two durable tight seating rubber check valves, and npt female inlet and outlet connections.