The BEECO In Line Dual Check Valve prevents the reverse flow of polluted water from entering into the drinking water supply. It is designed to be used in either the horizontal or vertical position and should be placed at the service entrance or can be used as a point of use device. This device is designed for continuous pressure applications in non-health hazard residential water system containment. It should be installed right after the water meter. Check with your local inspection authorities for installation requirements.