The 3/8" Watts Series SD-2 Dual Check Valves prevent the reverse flow of contaminated water, such as carbon dioxide gas and carbonated water, from entering into the potable water supply due to backpressure backflow. It consists of a stainless steel body construction with internal rubber components and is designed for continuous or intermittent pressure applications. Commonly found on tea and coffee makers this backflow carries the ASSE 1032 certification but does NOT carry the ASSE 1022 certification.