Backpressure Backflow – First Check Valve Fouled Open – Second Check Valve Holding Tight Relief Valve Opened Discharging

If the RPZ is in a backpressure state and water is continually discharge from the relief valve the first or second check valve may be fouled open. If the second check valve is holding tight against backpressure this situation is creating a no flow state within the RPZ and if water is coming out of the relief valve, the first check valve is most likely fouled open and high pressure is getting into the zone. If water is discharging out of the relief valve the RPZ is providing protection and is functioning as designed. If the second check valve is holding tight and water is discharging out of the relief valve, the RPZ is still providing protection since non-potable is not entering the potable water system.

To determine which check valve is not holding tight, close the downstream shut-off valve. If the downstream shut off valve is holding tight and water stops discharging from the relief valve, the second check valve is not holding tight. If the water continues to discharge from the relief valve after closing the downstream shut off valve, the first check valve is most likely fouled open, given that the downstream shut off valve is holding tight. To confirm that the first check valve is not holding tight, open test cock # 4. If after opening test cock #4, water stops discharging out of the relief valve or slows down, the first check valve is not holding tight. For this evaluation of the first check valve, the downstream shut-off valve would have to be confirmed to be drip tight.