RPZ test procedure, step by step.

Before you test: N.I.I.O.

Notify, Identify, Inspect and Observe, in that order, before a hose goes on.

Notify

• Tell the owner or whoever is on site that water past the assembly is about to go off, and for how long.
• Ask what is on the line before you close a valve: anything that cannot lose water or pressure, such as dialysis, boilers, medical or process equipment, livestock waterers or fire protection.
• Notify the water system too, if its program asks for notice before a test.

On an RPZ:

• Warn that the relief valve will dump water during the test. Have a bucket, towels and a clear discharge path ready.
• On a fire line, call the alarm monitoring company before you close a shut-off: the tamper switch will trip.

Identify

• Copy make, model, size and serial number off the assembly itself, not off last year's report. A swapped assembly is a new record.
• Record where it is on the premises.
• Confirm the assembly type matches the hazard the water system assigned to this connection.
• Confirm it is on the USC Foundation list of approved assemblies for the way it is installed.

On an RPZ:

• An RPZ is the high-hazard assembly. Confirm the hazard on this connection is what an RPZ is there for.

Inspect

• Inspect before you touch a valve. An assembly that is the wrong type, or installed wrong, fails no matter how it gauges.
• Both shut-off valves operate and hold.
• No visible leaks, cracks or freeze damage.
• Your test kit is in calibration. Most water systems want it calibrated within the last 12 months.

On an RPZ:

• Installed in the orientation it is approved for. Most RPZs are horizontal only.
• Relief port at least 12 in. above grade or flood level, discharging to an air gap.
• Not in a pit or vault that can flood the relief port.
• All four test cocks present, operable and not plugged.

Observe

• Watch the assembly at rest before you start: discharge, drips and noise all tell you something.
• Watch for thermal expansion on a closed system: a water heater downstream of a closed shut-off can spike the pressure.

On an RPZ:

• Is the relief valve discharging at rest? Continuous discharge points to the #1 check, or to the #2 check with backpressure. Intermittent discharge points to pressure swings.
• Note the flow direction arrow before you hook up: the high hose goes upstream of the #1 check.

TC is a test cock. SOV is a shut-off valve. psid is pounds per square inch, differential.

Pressurizing the gauge

1. FLUSH test cocks: open #4 TC and establish flow, then open TCs #3, #2, #1. Then close TCs #1, #2, #3 and #4.
2. ATTACH the high side hose to the #2 TC.
3. ATTACH the low side hose to the #3 TC.
4. PRESSURIZE the low side of the gauge by opening the #3 TC. Open the low bleed needle valve and let it flow.
5. PRESSURIZE the high side of the gauge by opening the #2 TC slowly. Open the high bleed needle valve and let it flow.
6. CLOSE shut-off #2.
7. CLOSE the high bleed needle valve, and allow the gauge reading to rise to the upper end of the scale.
8. CLOSE the low bleed needle valve.
9. OBSERVE whether the gauge reading remains above the relief valve opening point. Note it as the apparent differential pressure across the #1 check.
   • If the gauge reading drops to the low end of the scale and the relief valve discharges continuously, the #1 check is leaking. The rest of the test can't be completed.

Relief valve test

The relief valve must open before the differential pressure across check #1 is less than 2 psid.

10. OPEN the high side control needle valve at least one full turn.
11. OPEN the low side control needle valve slightly, no more than ¼ turn. This transfers pressure from the high side of the gauge into the zone of reduced pressure, to purposely equalize the differential pressure across the #1 check.
12. OBSERVE the gauge as it slowly descends to the relief valve opening point. Record the opening point when the first discharge of water is detected. Must be 2 psid or greater.
    • If the gauge drops below 2 psid and then the relief opens, or the gauge descends to zero and the relief doesn't open at all, record the relief valve as failing, but continue the test.
    • If the low control needle valve is opened a quarter turn and the reading does not decrease to the relief opening, shut-off #2 is leaking. Continuing requires a temporary bypass hose from the #1 TC to the #4 TC.
13. CLOSE the low control needle valve. Leave the high control needle valve open.

Check valve #2: tightness against backpressure

14. VENT air from the bypass hose by opening the bypass control needle valve, then close it.
15. ATTACH the bypass hose to the #4 TC, then open the #4 TC.
16. OPEN the low bleed needle valve, allowing the gauge needle to rise above the apparent differential pressure across the #1 check. Then close the low bleed needle valve and allow the gauge reading to stabilize.
17. OPEN the bypass control needle valve. This backpressures the #2 check with pressure from the high side of the gauge. If the gauge remains above the relief valve opening point, record the #2 check as tight on the test report.
    • If the gauge reading descends to steady relief valve opening, open the low bleed needle valve until the gauge rises above the apparent differential pressure across the #1 check, then close it. If the gauge descends to the relief opening point again, record the #2 check as leaking. The rest of the test can't be completed.
    • If the gauge reading stabilizes after closing the low bleed needle valve, record the #2 check as tight (disc compression was present).
    • If the gauge reading rises to the upper end of the scale when the bypass is opened, backpressure may be present. This could allow backflow through the gauge while it is connected. Close the #2 TC.
      • If the gauge reading stops rising or falls to the low end of the scale, it was a false backpressure indication, possibly from a pressure fluctuation. Open the #2 TC and continue the test.
      • If the gauge reading continues to rise with the #2 TC closed, backpressure is present. Close the #4 TC and record the #2 check as tight. Record the apparent differential pressure across the #1 check as actual, because there was no flow with the backpressure present. The relief opening was already recorded. The test is complete.

Check valve #1 test

Record the differential pressure across the #1 check now that the assembly is in a no-flow condition. The reading must be above the relief valve opening point and at least 5.0 psid.

18. OPEN the low bleed needle valve, allowing the gauge reading to rise above the apparent psid across check #1. Then close the low bleed needle valve and allow the gauge to stabilize. Record the value as the actual differential pressure across the #1 check.
19. CLOSE the TCs, detach the gauge, slowly restore customer service by slowly opening SOV #2, and complete the test report.

Failure matrix

What can go wrong at each step, what it means, and what goes on the report.

Troubleshooting an RPBA

Many problems are corrected by cleaning the internal components. Carefully observe the condition of the components. Shut-off valves can be re-opened and closed for a better seal. Use lubricants only to help reassemble components, and only non-toxic ones.

Other assemblies

• Double check test procedure →Double check valve assembly (DCVA)
• PVB test procedure →Pressure vacuum breaker assembly (PVBA)
• SVB test procedure →Spill-resistant pressure vacuum breaker assembly (SVBA)

All test procedures →

The software

• Bookings from a booking page, your own website, and an AI receptionist on your phone.
• Schedule board and route for each tester.
• Field app that scores every test, even with no signal.
• Test reports sent to the water system that serves each address.
• Card payments to your own Stripe account, and yearly renewals that charge after the test.
• Client portal for HOAs, property managers and contractors.
• $50/month flat: no per-test fee, no cut of payments.

• Every feature →What the app does, part by part.
• Compare →Next to other backflow and field-service software.
• Start free →No card. $50/month or $500/year once you go live, 45 days free.
• Free exam prep →Study questions, practice exams, device tests, a VR wet lab.

Contact

hello@backflowbase.com