Testing Procedures and Equipment
Test equipment
Testers use a differential pressure gauge test kit with high- and low-pressure hoses and bypass valves to measure check valve opening pressures and relief valve opening points. Know the gauge's accuracy and calibration requirements; an out-of-calibration gauge invalidates results. Always verify gauge zero and inspect hoses and fittings before testing.
Standard test sequence
For an RP assembly, the standard sequence is: (1) record supply and downstream pressures; (2) test the first check by isolating and measuring its hold; (3) test the second check; (4) test the relief valve opening differential; (5) confirm the relief valve reseats. For a DCVA, test each check valve for tightness and opening pressure. For a PVB/SVB, test the air-inlet opening and check valve. Record all readings and pass/fail against the manufacturer's or jurisdiction's criteria.
Traps
Common question traps: testing in the wrong order, failing to isolate sections, confusing opening pressure with hold pressure, and forgetting to record ambient conditions. Another trap: assuming a passing test proves installation compliance - orientation and drainage still matter. Safety: depressurize before disconnecting, avoid water damage, and never test a device not rated for field testing.
Rule of thumb
Test in the manufacturer's specified order, record every reading, and compare each to the acceptance criteria - do not rely on a single overall "pass."
Worked example: If the RP relief valve opens at a differential below the minimum, the assembly fails even if both checks hold; document the reading and tag it for repair.