Field Testing Procedures and Test Equipment
Test sequence and values
Field testing of an RPZ follows a defined order: (1) flush and inspect, (2) test the relief valve opening point, (3) test check valve 1 against backpressure, (4) test check valve 2. Record the differentials and compare to the assembly's published minimums. A common exam trap is testing in the wrong order or failing to isolate the relief valve before checking the checks. Know that test kits use a differential pressure gauge, and that hoses must be bled to remove air before readings are trusted.
For a DCVA, test each check separately, applying pressure in the direction of flow and confirming the check holds against reverse flow. For a PVB, test the air inlet opening and the check. For an AVB, test the air inlet opening.
Equipment care
Gauges must be calibrated; a common trap is a kit with a stale calibration sticker. Hoses must be inspected for cracks and the high-side/low-side connections must be correct. Always record the gauge serial number and calibration date on the report.
Worked example
An RPZ reads 8.0 psi across check 1 and 6.0 psi across check 2, with the relief opening at 2.0 psi differential. If the manufacturer requires a minimum of 5.0 psi across check 1 and 1.0 psi across check 2, both checks pass. If the relief opens below the required differential, the assembly fails and requires repair. Always compare to the manufacturer's published values, not to a generic number.