Troubleshooting, Repair, and Maintenance
Diagnose before you disassemble
On an RPZ, the relief valve is the messenger, not the culprit. Continuous discharge at no flow usually means check valve #1 is not seating (debris, worn disc, damaged seat, weak spring) or the relief seat itself is fouled. Discharge that appears only when downstream pressure builds points to check valve #2 leaking backward. Intermittent dribbling often reflects thermal expansion, water hammer, or supply pressure fluctuation rather than a failed part. Read the symptom pattern before opening the valve.
Common causes
Debris and scale on seats and discs; worn or swollen rubber; ruptured diaphragms; broken springs; freeze damage; corrosion pits; and pit flooding that submerges the relief port. On DCVAs, a single failed check is usually contamination or a damaged seat rather than a spring problem.
Repair practice
Use only manufacturer-approved repair kits; do not mix parts between models or substitute generic rubber. Clean and inspect seats, replace discs and springs as a set, torque to specification, and verify free movement of the check assemblies and the relief plunger. Any repair, relocation, or replacement requires a retest and a report to the AHJ - a repaired assembly is not "returned to service" until it passes.
Maintenance and traps
- Strainers upstream of the assembly must be cleaned; a clogged strainer causes low flow and false failures.
- Protect from freezing and from flooding; never install an RPZ in a floodable pit.
- Do not paint over relief ports, test cocks, or nameplate data.
- Trap: replacing the relief valve when the real fault is check #1.
- Trap: assuming a passed test means no maintenance is due.
Rule of thumb
"Symptom pattern first, parts second" - continuous discharge implicates check #1, pressure-dependent discharge implicates check #2. Worked example: after replacing check #1's disc and seat, retest the full assembly and file the report.