Why Is Water Leaking or Dripping From My Backflow Preventer?

Seeing water drip or stream from your backflow preventer can be alarming—especially with Los Angeles water rates and drought-conscious habits. The good news? Not every drip is an emergency.

In this guide, Atlas Backflow Services explains the most common reasons for leaks, how to tell what’s normal versus a problem, and when to call for professional Backflow Testing Los Angeles to stay compliant and protect your water supply.

When is leaking “normal,” and when is it a problem?

• Normal, short-term dripping: A brief drip after testing or after the irrigation system shuts off can be normal as pressure equalizes and debris flushes out.

• Abnormal, ongoing discharge: Continuous water from the relief port, heavy dripping that doesn’t stop, or water appearing from seams is a sign of a failing component, debris on a check valve, high pressure issues, or incorrect installation.

If you see steady flow or repeated discharges, schedule Backflow Testing Los Angeles right away. Atlas Backflow Services can diagnose and fix the root cause before you waste water or fail compliance.

How A Backflow Preventer Works (and why it might drip)

Backflow preventers stop contaminated water from reversing direction into your drinking water. Depending on the model, you’ll see different “normal” behaviors:

• RPZ (Reduced Pressure Zone) Assembly: Has a relief valve that intentionally opens to discharge water when it senses unsafe pressure conditions. Occasional spits can be normal; continuous flow is not.

• DCVA (Double Check Valve Assembly): No relief valve. Drips typically point to a leaking test cock, o-ring, or a check valve that isn’t sealing due to wear or debris.

• PVB (Pressure Vacuum Breaker): Often on irrigation. A small spit during startup can be normal, but ongoing leaking from the bonnet/air inlet indicates a worn spring, seal, or cracked bonnet.

The most common reasons your backflow preventer is leaking

1. Debris trapped in the check valve

   
   

   • Tiny particles from municipal water or a reopened service line can lodge in the check assembly, preventing a full seal and causing dripping or discharge.

   • Signs: Intermittent dripping that started after construction, a main line repair, or seasonal startup.

   • Fix: Professional cleaning/reseating of checks. Avoid running the device without a strainer if your system is prone to debris.

2. Thermal expansion or high incoming pressure

   • Closed plumbing systems without an expansion tank can see pressure spikes when water heats. High city pressure (often over 80 psi in parts of LA) also stresses devices.

   • Signs: Relief valve opens randomly, especially after hot water use; relief port discharges at night.

   • Fix: Install/repair an expansion tank; add or service a pressure reducing valve (PRV). Atlas Backflow Services can assess both during Backflow Testing Los Angeles.

3. Worn seals, o-rings, or check springs

   • Rubber components wear out with age, chlorine exposure, and cycling.

   • Signs: Persistent slow drip from test cocks, bonnet, or body seams; device older than 5–7 years without service.

   • Fix: Use manufacturer-specific rebuild kits and re-test to verify tightness.

4. Improper installation height or orientation

   • RPZs must be above grade with proper clearance and an air-gapped drain. PVBs must be above the highest downstream outlet, usually 12 inches or more.

   • Signs: Frequent nuisance discharge, water pooling around the unit, drain lines that are undersized or submerged.

   • Fix: Repositioning or correcting the drain/air gap to code. This is common in retrofits or DIY installs.

5. Freezing or heat damage

   • Uninsulated outdoor devices can crack in rare cold snaps; prolonged sun exposure degrades plastics and seals.

   • Signs: Hairline cracks, irregular spray, or leaks from the body itself.

   • Fix: Replace damaged parts or the device; add proper insulation and UV protection.

6. Downstream backpressure or backsiphonage

   • Elevation changes, pumps, or quick-closing valves downstream can create conditions that force the relief valve to open.

   • Signs: Relief valve opens when a pump kicks on or when high-elevation branches drain.

   • Fix: Check downstream check valves, add water hammer arrestors, or reconfigure piping as needed.

7. After-testing residual drip

   • Following annual testing, minor drips from test cocks can occur if caps aren’t seated perfectly or debris moved during the test.

   • Fix: Usually resolves quickly; if not, a simple reseat or new washer solves it. This is one reason to hire meticulous testers like Atlas Backflow Services.

A quick diagnostic checklist you can do safely

• Identify the device type: RPZ, DCVA, or PVB. Look for a relief port (RPZ/PVB) versus no relief (DCVA).

• Observe the leak point: Relief port, test cocks, bonnet seam, or body crack.

• Note the timing: Only during irrigation? After water heater cycles? Random?

• Check system pressure context: Do you have a PRV? An expansion tank? When were they last serviced?

If you see steady discharge from an RPZ’s relief port or persistent leaking from any device, do not plug, cap, or route the discharge into a sealed pipe. This is a safety device—restricting flow can be dangerous and violate code.

What to do next (and what to avoid)

• Do:

  • Turn off downstream valves to see if the leak stops, which helps isolate the problem.

  • Schedule professional Backflow Testing Los Angeles with Atlas Backflow Services to verify performance and capture required test reports for your water purveyor.

  • Ask for a pressure and expansion assessment to prevent repeat issues.

• Avoid:

  • Plugging or taping over a relief port.

  • Disassembling the device without proper kits and gauges.

  • Ignoring continuous discharge—many LA jurisdictions require immediate repair and re-test.

Preventative maintenance for Los Angeles properties

• Annual testing (or as required by your water purveyor): LADWP and surrounding agencies typically require yearly tests with certified results.

• Routine rebuilds: Many manufacturers recommend rebuilding RPZs and PVBs every 3–5 years, depending on water quality and usage.

• Install strainers where appropriate: Especially helpful after new construction or when sediment is common.

• Keep devices protected and accessible: Insulate outdoors, shield from direct sun, and maintain proper clearance for testing and draining.

• Verify PRV and expansion tank health: These two components dramatically reduce nuisance discharges and extend device life.

Atlas Backflow Services can bundle your annual Backflow Testing Los Angeles with a pressure survey and expansion tank check to prevent surprise leaks and violations.

Repair vs. replacement: How we decide

• Repair/rebuild if the body is sound and parts are readily available. Rebuild kits often restore factory performance.

• Replace if the body is cracked, obsolete, corroded beyond spec, or repeated failures occur despite proper pressure control.

• Document and certify: After any repair or replacement, we perform a full test and file the results with your water provider as required.

Why choose Atlas Backflow Services

• Certified specialists: Focused exclusively on cross-connection control and Backflow Testing Los Angeles.

• Code-first approach: We adhere to USC Foundation for Cross-Connection Control standards and local Los Angeles requirements.

• Fast, tidy, and transparent: Clear cause-and-effect explanations, photos if requested, and no-surprise estimates.

• Compliance handled: We submit test reports to your water purveyor and remind you ahead of renewals to avoid fines.

Final takeaway

A little drip from a backflow preventer can be normal in specific moments, but continuous leaking signals a pressure, debris, wear, or installation issue. The safest path is a certified test and targeted fix.

Atlas Backflow Services is your local partner for reliable, compliant Backflow Testing Los Angeles—keeping your system tight, safe, and up to code while minimizing water waste.