The Principle Operation of a Hose Connection Dual Check Valve Vacuum Breaker – Backflow Prevention Device – Continuous Pressure and Backpressure
The HCDCV shall not be used where there is backpressure greater than 4.3 psi or where continues use would exceed more than 12 hours. If downstream shut-off valve are to be used on the end of a hose connection, such as spray nozzle, the water supply shall be closed at the sill cock and the pressure in the hose released by opening the spray nozzle. Pressurized hoses may create a constant pressure greater than 4.3 psi for more than 12 hours which may cause the atmospheric vent to malfunction. If the atmospheric vent is stuck closed or malfunctions the HCDCV is inoperative and not providing protection. The HCDCV is limited to low-head backpressure and since backpressure is an issue, the HCDCV should be tested periodically or at least annually to determine if the second check valve is operational. The second check valve is the primary protection when backpressure is present. ASSE has in-line field test procedure for the HCDCV.
