Why Is The Relief Valve On My RP (Reduced Pressure) Assembly Discharging Water?

If you’re seeing water dumping or dripping from the relief valve on your RP (reduced pressure) assembly—also called an RPZ—you’re witnessing the device doing its job: protecting your drinking water.

But continuous discharge is a red flag that something’s off. In this guide, Atlas Backflow Services explains why RPs release water, the most common causes of nuisance discharge, and how timely Backflow Testing Los Angeles can pinpoint the fix and keep you compliant.

Normal vs. Problem Discharge

• Normal, brief discharge: A short spit during startup/shutdown or after a test can be normal as pressure stabilizes.

• Problem discharge: Steady flow, recurring dumps, or discharge that won’t stop indicates debris, worn internals, high or fluctuating pressure, downstream backpressure, or installation issues.

If your RP’s relief valve runs more than a brief moment—or repeatedly throughout the day—schedule professional Backflow Testing Los Angeles with Atlas Backflow Services.

How an RPZ works (in 20 seconds)

An RP assembly contains two check valves with a “reduced pressure zone” between them. A relief valve monitors that middle zone. If upstream pressure drops, downstream pressure rises, or a check doesn’t seal, the relief valve opens to dump water to atmosphere — creating a safe barrier so contaminated water can’t backflow into your potable system. In short: when conditions aren’t safe, it discharges on purpose.

Top reasons your RP relief valve is discharging

1. Debris on a check valve seat

   • Tiny grit or scale can lodge on the first or second check, preventing a tight seal and raising zone pressure.

   • What you’ll see: Intermittent or continuous discharge that began after construction, a water main repair, or seasonal irrigation startup.

   • Fix: Disassemble, clean, and reseat checks; replace rubber parts as needed. After repairs, verify with certified Backflow Testing Los Angeles.

2. Worn rubber parts, springs, or relief valve components

   • Rubber discs, o-rings, and springs degrade over time due to chlorine, heat, and cycling.

   • What you’ll see: Persistent dripping or a relief valve that opens at lower-than-normal differentials.

   • Fix: Install a manufacturer rebuild kit for checks and relief valve. Re-test to confirm proper differential pressures.

3. Excessive or fluctuating supply pressure

   • Many Los Angeles neighborhoods see static pressures over 80 psi. Without a healthy PRV (pressure reducing valve), spikes and surges can force the relief valve to open.

   • What you’ll see: Discharge during high-demand periods, after water hammer events, or randomly—especially at night.

   • Fix: Service or install a PRV and, where appropriate, water hammer arrestors. Atlas Backflow Services can assess both during Backflow Testing Los Angeles.

4. Thermal expansion and closed-system backpressure

   • When water heats in a closed system (check valves, PRV), it expands, increasing downstream pressure and pushing back against the RP.

   • What you’ll see: Relief valve opens after long hot water use or overnight.

   • Fix: Install or replace an expansion tank and ensure it’s properly charged. This is a common nuisance discharge root cause.

5. Downstream backpressure or backsiphonage

   • Pumps, elevation changes, or downstream valves closing abruptly can create pressure conditions that lift the relief valve.

   • What you’ll see: Relief discharge when an irrigation pump starts, a booster kicks on, or high-elevation fixtures drain.

   • Fix: Evaluate downstream equipment, add check valves or arrestors as needed, and verify correct RP sizing.

6. Improper installation or drainage

   • RPs must be installed above grade, horizontally, and with a proper air-gapped drain. Incorrect orientation or submerged drains can cause nuisance discharge and safety hazards.

   • What you’ll see: Frequent discharges, water pooling around the device, or drain lines that can’t keep up.

   • Fix: Correct mounting height/orientation and provide a code-compliant, air-gapped drain sized for full relief flow.

7. Freeze or heat damage (yes, even in SoCal)

   • Rare cold snaps, sun exposure, or UV-degraded plastics can crack bonnets or warp seats.

   • What you’ll see: Irregular sprays, body leaks plus relief valve activity.

   • Fix: Repair or replace damaged components and add insulation/UV shielding.

8. Wrong device for the job or wrong size

   • Undersized RPs or the wrong model for your flow profile can chatter and discharge.

   • What you’ll see: Relief valve opens during high flow; nuisance discharge tied to peak irrigation or process demand.

   • Fix: Verify sizing and select a model matched to your flow and pressure conditions.

Safe checks you can do before calling

• Observe the leak point: Confirm water is from the relief port (center “spout”) and not a test cock or seam.

• Note timing and triggers: Startup? After hot water use? When pumps run? Random?

• Look for a PRV and expansion tank: If missing—or older than 5–7 years—these are prime suspects.

• Check the drain and air gap: Ensure the relief discharge isn’t restricted or submerged.

Important: Never cap, plug, or pipe the relief port into a sealed drain. The relief must discharge freely to atmosphere. Improper modifications are unsafe and violate code.

What professional testing reveals

A certified tester from Atlas Backflow Services will:

• Gauge the device: Verify differential pressures across checks and the relief opening point.

• Isolate the culprit: Determine whether the first check, second check, or relief is failing—and whether upstream/downstream conditions are to blame.

• Document compliance: Produce the official test report your water purveyor requires. If repairs are needed, we’ll provide a clear estimate and perform re-testing post-repair.

This is the core value of expert Backflow Testing Los Angeles: fast diagnosis, targeted repair, and paperwork handled.

Repairs, prevention, and long-term reliability

• Targeted rebuilds: Most discharge issues are resolved with manufacturer rebuild kits for checks and the relief valve, followed by precise reassembly and testing.

• Pressure control: A healthy PRV and properly charged expansion tank dramatically reduce nuisance discharges and extend RP life.

• Debris management: Upstream strainers (where allowed) and system flushing after construction or main repairs help keep checks clean.

• Annual compliance testing: Los Angeles-area purveyors typically require yearly certification. It’s the best time to catch worn parts before they cause a flood—or a violation.

• Environment-proofing: Insulate outdoor assemblies, shield from UV, and keep the area clear for service and drainage.

Atlas Backflow Services can bundle Backflow Testing Los Angeles with a pressure survey and expansion tank check to stop repeat problems at the source.

FAQs we hear in Los Angeles

• Is some dripping OK? A brief spit during pressure changes can be normal. Continuous or frequent discharge is not—get it tested.

• Can I route the relief line into a drain? Only to a code-compliant, air-gapped receptor sized for full relief flow. Never to a sealed or undersized line.

• Do I need a new device? Usually not. Most issues are resolved with a rebuild and pressure corrections. We recommend replacement only for cracked/obsolete bodies or repeated failures.

Why choose Atlas Backflow Services

• Specialists in Backflow Testing Los Angeles: Certified, local, and focused on cross-connection control.

• Code-first approach: Aligned with USC Foundation for Cross-Connection Control and local purveyor requirements.

• Transparent diagnostics: Clear explanations, photos on request, and no-surprise pricing.

• Compliance handled end-to-end: From testing to repairs and filing, we keep you on schedule and out of trouble.

Final takeaway

An RP relief valve discharges to protect your water—but ongoing flow signals a correctable problem: debris, worn internals, pressure spikes, or system backpressure. The fastest, safest path is a certified test and targeted fix.

Schedule Backflow Testing Los Angeles with Atlas Backflow Services to diagnose the cause, restore proper operation, and keep your property compliant—without wasting water or risking contamination.Ready to stop the discharge the right way? Contact Atlas Backflow Services today.