Leak location
Backflow preventer leaking from the vent: do not plug the discharge
Use the device family, exact opening, flow severity, timing, pressure events, and freeze history to choose the safe next route.
An RPZ relief valve and a PVB air inlet are different mechanisms. Continuous discharge can reflect debris, pressure conditions, failed internals, or damage and needs the correct device-specific service.
Never cap, plug, pipe shut, or obstruct a relief or air opening. Protect people and property from flooding, spray, and ice.
Interactive check
Turn observations into a next step
This narrows the route. It does not replace an on-site test, manufacturer instructions, or local requirements.
Evidence sequence
Move in this order
- 01
Identify the assembly
Use the full body shape, test cocks, bonnet, relief location, and model label.
- 02
Record the event
Capture severity, duration, pressure changes, valve work, and weather.
- 03
Close the compliance loop
Repair or replacement may require a passing retest and accepted report.
Identification notes
What to look for
- RPZ relief discharge exits below the zone between two checks.
- PVB venting exits around the raised bonnet or air inlet.
- A crack or fitting leak is not the same as intentional discharge geometry.
Safe observations
What you can check without taking it apart
- Keep the opening unobstructed.
- Move vulnerable property away from discharge if safe.
- Record the model and exact exit point.
Stop conditions
Move to qualified help when
- Forceful continuous discharge
- Flooding or ice hazard
- Cracked body
- Fire or high-hazard service
Boundary check
Do not confuse this path with
- A threaded fitting leak follows a different repair path.
- A pressure regulator bell leak is not a backflow relief event.
- A sewer backwater valve does not discharge potable supply water.
Official local layer
Your utility sets the rule
The page distinguishes observable device geometry and urgency. Only a qualified test and manufacturer procedure can confirm the failed component.
Evidence ledger
What this decision path is built on
The page distinguishes observable device geometry and urgency. Only a qualified test and manufacturer procedure can confirm the failed component.
- 01U.S. EPA · EPA-CCC-001Cross-Connection Control ManualBackflow, backsiphonage, device families, hazard protection, testing, and program responsibility. Verified 2026-08-02.
- 02Watts · WATTS-RPZ-009Series 009 reduced pressure zone assemblyRPZ construction, relief discharge, installation constraints, service literature, and local-code warning. Verified 2026-08-02.
Continue the case
Related next steps
CONTENT REVIEWED · 2026-08-02