The Principle Operation of a Dual Check Valve with Intermediate Atmospheric Vent – Backflow Prevention Device – No Flow or Static State
This DCVwIV contains an intermediate atmospheric vent positioned between two spring-loaded check valves. In a no-flow state, the DCVwIV is pressurized. The check valves since they are spring loaded will close automatically under a no-flow condition. The intermediate atmospheric vent is held closed by the action of the diaphragm seal that directly responds to the water pressure. The positive water pressure holds the diaphragm seal in place to close off the atmospheric vent. If no water is flowing through the DCVwIV but is pressurized, both check valves are closed tight and the atmospherics vent closed.