Watts 0072203 1/2″ dual check valve this 1/2 by 1/2 in lead free dual check valve prevents the reverse flow of polluted water from entering into the drinking water supply at the service entrance or at individual outlets. This valve consists of a lead free brass body construction, with two plastic replaceable check valves and stainless steel springs. It is designed for non-health hazard residential water system containment, continuous pressure applications and is to be installed immediately downstream of the residential water meter, in a vertical or horizontal position. The minimum working pressure is 10 psi (69 kpa) and maximum working pressure is 175 psi (12 bar).