What should I do if my backflow preventer freezes or was submerged during a flood?

When a backflow preventer freezes or goes under floodwater, your drinking water safety is at stake. A compromised device can allow contaminated water to flow backward into your home or business and into the public supply.

Below is a clear, practical plan our backflow testing San Diego experts recommend to minimize risk and get you back in compliance quickly.

Quick answer: Immediate steps to take

• Shut off water to the device at the nearest isolation valve. If you can’t find it, shut off the main.

• Do not drink or use water for cooking if the device was submerged or is visibly damaged. Use bottled water until testing confirms safety.

• Drain the device if it’s frozen: open test cocks and downstream faucets to relieve pressure and allow thawing without bursting.

• Do not apply open flame/torches to thaw. Use ambient warmth or gentle, indirect heat.

• Document the damage with photos for your water provider and insurance.

• Call Atlas Backflow Services to test, repair, or replace before you put the system back in service.

This is the exact protocol our backflow testing San Diego experts recommend after freeze or flood conditions in Southern California.

Why this matters in San Diego

San Diego’s microclimates make both risks real: inland cold snaps can crack devices overnight, while intense winter storms and king tides can flood vaults and irrigation assemblies.

A damaged Reduced Pressure (RP) assembly, Double Check Valve Assembly (DCVA), or Pressure Vacuum Breaker (PVB) can’t protect you from backflow. Local jurisdictions require these devices to be tested after any event that may impair performance—and annually thereafter.

How to tell if your backflow preventer is damaged

• Visible cracks or leaks on the bronze body, bonnet, or relief valve

• Water constantly discharging from the RP relief port

• Broken test cocks, blown caps, or missing freeze plugs

• No flow or reduced pressure to fixtures downstream

• Device or vault was fully or partially submerged

If you notice any of these, do not operate sprinklers, process water, or fire systems protected by the device until it’s tested. That’s a key safety step our backflow testing San Diego experts recommend in all emergency calls.

If your backflow preventer froze

1. Shut off and depressurize

   • Close upstream and downstream shutoff valves.

   • Open all four test cocks and a downstream faucet to relieve pressure.

2. Thaw safely

   • Use ambient heat, towels soaked in warm water, or a space heater pointed near—but not directly at—the assembly.

   • Avoid open flames or excessive heat that can warp elastomers and springs.

3. Inspect for obvious damage

   • Look for splits in the body/bonnet, frost heave damage, or cracked relief valves.

   • PVBs often crack at the bonnet/cap; RPs may show relief valve dumping.

4. Do not re-pressurize yet

   • Re-pressurizing a damaged device can worsen cracks or flood the area.

5. Schedule professional testing and repair

   • A certified tester will perform check valve, relief valve, and shutoff tests with a calibrated differential gauge, and replace rubber kits or assemblies as needed.

Our backflow testing San Diego experts recommend replacing rubber parts (seats, checks, diaphragms) after freeze events even if the body looks intact—freeze cycles can micro-damage elastomers that later fail under load.

If your backflow preventer was submerged during a flood

1. Consider the water unsafe

   • Floodwater carries sediment, chemicals, and pathogens. Do not drink, cook, or process with water downstream of the device until cleared.

2. Isolate the device

   • Close shutoffs and leave the assembly out of service until testing.

3. Do not disassemble on your own

   • Contamination and code compliance require a certified professional to clean, disinfect, and test.

4. Professional service steps

   • Remove debris/sediment from the body and test cocks.

   • Disinfect interior components, replace rubber parts as needed, and test each check/relief for proper differential.

   • Verify the relief valve on RPs opens and reseats at correct pressures; flood silt can prevent proper sealing.

   • Issue a test report for your water provider.

5. When replacement is prudent

   • If the bronze body is cracked or heavily corroded, or if repeated tests fail after cleaning, replacement is the safest and often fastest path to compliance.

Based on manufacturer guidance and local practices, our backflow testing San Diego experts recommend full testing and disinfection of any device that was submerged—even if it appears to function—before it’s returned to service.

Device-specific notes

• RP (Reduced Pressure) assemblies: The relief valve is the heart of protection. Flood silt or freeze damage can make it discharge continuously or fail closed. Test and rebuild kits are common; replacement may be faster for severe damage.

• DCVA (Double Check): Flooding can lodge debris on check seats causing backflow under low pressure differentials. Precise testing is essential before reuse.

• PVB (Pressure Vacuum Breaker): Most freeze-prone due to elevated installation. Bonnet/float assemblies often crack—frequently a replace vs. repair decision.

Compliance in the San Diego area

• Annual certification is required by most local agencies, including the City of San Diego Public Utilities Department. Events like freezing or flooding trigger a post-incident test before returning to service.

• Commercial, irrigation, and fire line backflow devices may have stricter timelines.

• Keep your dated photos, test reports, and invoices for insurance or municipal records.

If you’re unsure of your specific requirements, our backflow testing San Diego experts recommend calling your water purveyor—or just ask us, and we’ll look it up for your address.

Prevent it next time

• Insulate and cover: Use approved insulation covers for above-ground assemblies. Do not block the RP relief discharge path.

• Drain for cold snaps: For irrigation PVBs/DCVAs, shut off upstream, open test cocks, and drain ahead of forecast freezes.

• Raise and vent vaults: Ensure drainage is clear; add risers or relocate devices out of flood-prone pits when feasible.

• Annual service: Proactive rubber kit replacements extend life and reliability.

• Smart irrigation controls: Set “rain/freeze” modes to avoid pressurizing devices during adverse weather.

These are practical steps our backflow testing San Diego experts recommend for homeowners, property managers, and facility teams across the county.

Why choose Atlas Backflow Services

• Certified and experienced: ASSE-certified testers with specialized training in RP, DCVA, and PVB diagnostics.

• Fast emergency response: Priority scheduling after storms and cold snaps across San Diego County.

• Repairs and replacements: OEM kits on hand for most models, plus full device swaps when time is critical.

• Clear documentation: We file test reports with your water provider and provide records for insurance.

At Atlas Backflow Services, our mission is simple: protect your water, meet code, and minimize downtime. When in doubt, follow what our backflow testing San Diego experts recommend—shut it down, don’t drink the water, and get a certified test before you turn anything back on.

Ready to get help?

• Call Atlas Backflow Services to schedule an urgent test, repair, or replacement.

• Ask about storm and freeze-readiness audits for your property.

• Serving homes, HOAs, commercial sites, and fire protection systems throughout San Diego County.

Your water safety can’t wait. If your backflow preventer froze or was submerged, contact Atlas Backflow Services today and get compliant, fast.