When an RPZ (Reduced Pressure Zone) backflow preventer is found discharging from the relief valve, it does not always mean the valve is faulty. The relief valve is designed to discharge when the internal pressure differential is compromised. Follow the steps below to properly diagnose the issue:

Step 1 – Determine the Type of Discharge

First, observe the relief valve carefully.

Is the discharge steady and consistent?

• Steady, continuous drip or flow
  This indicates an internal component issue. Proceed with the troubleshooting steps below.

• Intermittent, surging, or random discharge
  The RPZ is likely operating correctly. The system may be experiencing pressure fluctuations such as:

  • Thermal expansion in a closed system

  • Supply pressure spikes

  • Quick-closing valves

  • Water hammer conditions

If the discharge is steady and consistent, continue to Step 2.

Step 2 – Check the 2nd Check Valve

1. Shut off the downstream shut-off valve.

2. Observe the relief valve discharge.

If the discharge stops:
The 2nd check valve is fouled or faulty.

• Remove the cover above the check assemblies.

• Inspect for debris, damaged rubber, worn seats, or broken springs.

• Clean or replace components as necessary.

If the discharge continues:
Proceed to Step 3.

Step 3 – Check the 1st Check Valve

1. Create a flow condition equal to or greater than the relief valve discharge (open a downstream fixture or test port).

2. Observe the relief valve discharge.

If the discharge stops while water is flowing:
The 1st check valve is fouled or faulty.

• Remove the bronze cover above the checks.

• Inspect for debris or damaged components.

• Clean or replace parts as required.

If the discharge continues while water is flowing:
Proceed to Step 4.

Step 4 – Inspect the Relief Valve Assembly

If the relief valve continues to discharge under flow conditions, the relief valve assembly is likely faulty.

• Remove the relief valve from the body.

• Inspect the diaphragm, spring, and internal components.

• Remove debris and check for wear or damage.

• Replace faulty parts as needed.

• NOTE THERE COULD BE MORE THAN ONE ISSUE (CHECK VALVE MAYBE FAILED ALSO)

Common Causes of RPZ Relief Valve Discharge

• Debris lodged in check valves

• Worn or damaged check discs

• Damaged relief valve diaphragm

• Spring failure

• Pressure fluctuations within the system

• Improper installation or orientation

Final Notes

An RPZ relief valve is designed to discharge when necessary to protect the potable water supply. Always determine whether the discharge is steady (mechanical issue) or intermittent (system pressure issue) before disassembling the valve.

Proper diagnosis saves time, reduces unnecessary rebuilds, and ensures the device continues protecting the water supply as intended.