What Parts Are Commonly Replaced in a Backflow Repair?

When your backflow preventer fails a test or starts showing signs of wear, the good news is that most issues don't require a full device replacement.

In most cases, a skilled technician can restore your assembly to full working order by replacing a handful of specific internal components.

Understanding which parts are commonly replaced—and why—helps property owners make informed decisions and avoid unnecessary expenses.

At Atlas Backflow Services, our backflow testing experts in Orange County recommend learning the basics of your assembly so you can communicate effectively with your repair technician and budget appropriately for maintenance.

Below, we'll walk through the most commonly replaced backflow parts, why they fail, and what you can expect during a typical repair.

Why Backflow Devices Need Repair in the First Place

Backflow assemblies are mechanical devices with moving parts exposed to constant water pressure, temperature changes, mineral deposits, and debris.

Over time, even high-quality components wear out.

Common causes of failure include:

• Hard water mineral buildup that prevents valves from sealing properly

• Rubber component degradation due to age and chlorine exposure

• Debris contamination from pipe sediment or construction work

• Freeze damage when devices aren't properly winterized

• Pressure surges that stress internal mechanisms

Our backflow testing experts in Orange County recommend annual testing not only because it's legally required, but because early detection of worn parts can prevent a complete device failure and a much costlier repair.

1. Rubber Seals and O-Rings

By far the most commonly replaced parts in any backflow repair are rubber seals and O-rings. These small but critical components create watertight closures throughout the assembly.

Over time, rubber hardens, cracks, or compresses, leading to leaks and failed pressure tests.Signs that seals need replacement:

• Visible water leakage from the assembly

• Failed annual test with pressure differential issues

• Audible dripping when the device is pressurized

Replacement is relatively inexpensive and quick. Our backflow testing experts in Orange County recommend using manufacturer-approved seal kits rather than generic alternatives, as off-brand rubber components often fail prematurely.

2. Check Valves

Check valves are the heart of any backflow preventer. They allow water to flow in one direction while blocking reverse flow.

Most assemblies contain at least one or two check valves, and these are among the most frequently repaired or replaced components.Check valve issues typically involve:

• Worn or torn rubber discs that can't seal completely

• Damaged springs that fail to close the valve fully

• Corroded or scratched seats preventing a tight seal

• Debris lodged between moving parts

A check valve repair usually involves replacing the rubber disc, spring, and seat as a complete kit.

Our backflow testing experts in Orange County recommend replacing both check valves at the same time, even if only one has failed, since they're typically the same age and the second is likely close behind.

3. Relief Valves

Found primarily in Reduced Pressure Zone (RPZ) assemblies, the relief valve is a safety mechanism that discharges water if pressure conditions become unsafe.

It's also one of the most failure-prone components, especially in older devices.Common relief valve replacements include:

• Diaphragm assemblies that crack or stretch over time

• Relief valve springs that weaken with use

• Seat rings that erode from constant water exposure

A failing relief valve often manifests as continuous water discharge from the bottom of the device.

If you notice persistent dripping or pooling water beneath an RPZ assembly, our backflow testing experts in Orange County recommend scheduling immediate service to prevent both water waste and compliance violations.

4. Springs

Internal springs maintain proper tension on check valves and relief valves, ensuring they open and close at the correct pressure thresholds. Springs can lose tension over time, become corroded, or break entirely.When springs fail, the device may still appear functional but won't pass a calibration test.

This is why visual inspection alone is never enough—certified testing equipment is required to identify weak springs. Our backflow testing experts in Orange County recommend replacing springs whenever a complete check valve rebuild is performed.

5. Test Cocks

Test cocks are small valves on the side of the assembly used by certified testers to attach pressure gauges. While they don't affect day-to-day function, damaged test cocks can leak or make annual testing impossible.

Common test cock issues include:

• Stripped threads from over-tightening

• Frozen or seized handles

• Internal corrosion from disuse

• Broken handles from impact

Replacing a test cock is one of the simplest backflow repairs and is often performed during routine maintenance.

6. Shutoff Valves (Ball Valves or Gate Valves)

Each backflow assembly has shutoff valves on both the inlet and outlet sides. These allow water to be isolated for testing or repair. Over years of use—or worse, years of disuse—these valves can seize, leak, or fail to fully close.

Replacing shutoff valves is a more involved repair because it often requires shutting down the main water supply temporarily.

Our backflow testing experts in Orange County recommend exercising shutoff valves at least once a year to prevent them from seizing in place.

7. Bonnets and Covers

The bonnet is the top cover of a check valve or relief valve assembly. While durable, bonnets can crack from freeze damage, impact, or corrosion. A cracked bonnet typically requires complete replacement and may necessitate replacing the gaskets beneath it as well.

8. Internal Cartridges and Modules

Many modern backflow devices use modular cartridge designs that allow technicians to replace entire internal assemblies as a single unit. This approach is faster and often more reliable than replacing individual components.Cartridge replacement is especially common for:

• Wilkins and Watts RPZ devices

• Febco double check assemblies

• Newer commercial-grade preventers

While cartridges cost more upfront, our backflow testing experts in Orange County recommend them for high-traffic commercial properties because they minimize downtime and extend the overall service life of the assembly.

When Repair Isn't Enough: Full Device Replacement

Sometimes parts replacement isn't the most cost-effective solution. If your device is more than 15 years old, has experienced multiple failures, or is no longer manufactured (making parts hard to source), full replacement may be smarter.

Signs that replacement beats repair:

• Repeated test failures even after part replacements

• Cracked or corroded body castings

• Obsolete model with discontinued parts

• Repair cost exceeds 50% of replacement cost

Our backflow testing experts in Orange County recommend a full assessment before approving any major repair. A qualified technician will weigh the cost of parts, labor, and likely future failures against the price of a new, more efficient device.

Trust Atlas Backflow Services for Quality Repairs

Whether your backflow device needs a simple O-ring replacement or a complete check valve rebuild, the quality of parts and workmanship matters. At Atlas Backflow Services, we use only manufacturer-approved components, employ AWWA-certified technicians, and stand behind every repair with reliable service guarantees.

Don't let a small worn part turn into a major compliance headache. If your backflow device is due for testing, showing signs of leakage, or has already failed an inspection, contact Atlas Backflow Services today.

Our team will diagnose the issue, recommend the right repair, and get your assembly back in compliance—quickly, affordably, and right the first time.