Recommended Testing - Reduced Pressure Backflow Preventers

Testing for Loading on the #2 Check Valve

  1. Close all valves on tester.
  2. Close #2 shut-off valve on backflow preventer.
  3. Install high-pressure hose on test cock #3.
  4. Install low-pressure hose on test cock #4.
  5. Open test cocks #3 and #4.
  6. Bleed all air from tester and hoses. Bleed low side last to establish a pressure differential. Close low-side bleeder slowly.
  7. Gauge must indicate at least 1 psid (record on test report under check valve #2). If below 1 psid, the check is leaking or the spring is too weak.
  8. Close test cocks and remove test equipment. Close all valves on tester.

Testing Check Valve #2 Against Reverse Flow and Shut-off

  1. Install high-pressure hose on test cock #2.
  2. Install low-pressure hose on test cock #3.
  3. Open test cocks #2 and #3.
  4. Bleed all air from tester and hoses. Close low side last and slowly to establish differential pressure.
  5. Attach by-pass hose to test cock #4 and open test cock #4.
  6. Open high-pressure and by-pass vent valves on tester.
  7. Gauge must not drop to the point where the relief valve leaks or check valve #2 leaks.
  8. If gauge holds at 5 psid or higher, record as “check valve #2 closed tight.”
  9. Close test cock #2. Gauge must remain steady and not drop to 0 psid. If it does, #2 shut-off valve is leaking and must be repaired. Accurate testing cannot occur if flow is present. (Record in comments.)

Testing #1 Check Valve

  1. Close by-pass valve on tester.
  2. Close test cock #4 and remove by-pass hose.
  3. Open test cock #2.
  4. Re-establish differential pressure by bleeding the low-pressure side. Gauge must hold 5 psid or higher (record under check valve #1). Indicates check valve #1 is holding tight.

Testing for the Opening Point of the Relief Valve

  1. With by-pass valve closed and high-side valve open on tester, slowly open the low-pressure valve. Watch for the first drip from the relief valve and record the gauge reading.
  2. Relief valve must open above 2 psid.
  3. There must be at least 3 psid difference between the loss across check valve #1 and the opening point of the relief valve.

NOTE: Line pressure fluctuations can cause problems when testing. It may be necessary to schedule testing when pressures are steadier.

Back to top