RPZ Test Procedure
Step-by-step RPZ testing - relief valve opening point, check valve differentials, isolation sequence, and pass/fail criteria.
- Perform the complete RPZ test sequence in the correct order
- Test the relief valve opening point and interpret the reading
- Test Check #2 and Check #1 differentials independently
- Apply RPZ pass/fail criteria to field test results
- Explain why the RPZ test begins with closing the downstream shutoff valve
Leçon 1
RPZ Test Setup & Pressure Isolation
Before You Begin
The RPZ test requires isolating the assembly from downstream demand so that pressure readings are stable and accurate. The test sequence must be performed in a specific order - deviating from the order produces incorrect readings.
Before starting:
- Verify the assembly is an RPZ and note the manufacturer, model, and size
- Identify all four test cocks (#1, #2, #3, #4) and both shutoff valves
- Flush hoses and connect them to the test kit
- Ensure the gauge is calibrated and zeroed
Step 1 - Close the Downstream Shutoff Valve
The first step in every RPZ test is to close the downstream shutoff valve (#2). This isolates the assembly from downstream demand and creates a static (no-flow) condition needed for accurate testing.
Why Downstream First?
Closing the downstream shutoff valve first ensures that water demand from the building does not affect gauge readings. If you close the upstream valve first, the pressure in the zone and downstream will equalize as water flows out, and you will not get accurate differential readings.
Step 2 - Bleed and Equalize
After closing the downstream shutoff:
- Connect the high-side hose to test cock #1 (upstream of Check #1)
- Connect the low-side hose to test cock #2 (in the reduced pressure zone)
- Open both test cocks and bleed air from the hoses
- Verify the gauge reads the correct differential across Check #1
Always begin the RPZ test by closing the downstream shutoff valve to isolate the assembly from demand. Connect hoses, bleed air completely, and verify gauge function before proceeding to the relief valve test.