What Should I Do If My Backflow Preventer Freezes or Was Submerged During a Flood?

Los Angeles doesn’t see blizzards often, but overnight cold snaps and high-desert winds can still freeze exposed plumbing. And with atmospheric rivers and flash floods hitting Southern California more frequently, submersion is a growing risk—especially for low-lying or street-side installations.

If your backflow preventer freezes or ends up underwater, quick, correct action protects your water quality, your property, and your compliance status.

Below, Atlas Backflow Services shares what our Backflow Testing Los Angeles experts recommend so you can act fast, avoid bigger damage, and get certified again without delay.

At a Glance: First Steps for Freeze or Flood

• Shut off water to the assembly at the upstream valve. If an RPZ is discharging or a pipe split, also shut the downstream valve.

• Do not operate the device (don’t cycle valves or test cocks) until it’s inspected. Moving frozen parts can cause cracks.

• Document the condition with photos/videos of the device, surroundings, and water level marks.

• Call a certified tester/repairer. Our Backflow Testing Los Angeles experts recommend scheduling an inspection, test, and repair/rebuild as needed before reactivation.

• Notify your water purveyor if your notice required testing, or if a fire line is affected.

If Your Backflow Preventer Froze

Freezing expands water inside the body, bonnets, and ball valves. Even if it “looks fine,” hairline cracks can cause leaks and failures under pressure.What to do next:

• Thaw slowly and safely. Use ambient heat: an insulated enclosure, space heater at a safe distance, or warm towels. Never use open flames or direct high heat (torches/heat guns) that can warp components or ignite enclosures.

• Check for obvious damage. Look for split ball valves, bulged bonnets, leaking test cocks, or cracked relief valve housings (on RPZs).

• Do not pressurize until tested. Once thawed, our Backflow Testing Los Angeles experts recommend a full test. Pressurizing a cracked assembly can cause sudden discharge and property damage.

• Plan for rebuilds. Rubber parts (checks, diaphragms, O‑rings) and springs often deform after freeze events. A rebuild kit returns internal tolerances to spec. Ball valves and test cocks may need replacement.

• Replace if the body is cracked. If the casting is compromised, replacement is the safe, code-compliant option.

Prevention after a freeze:

• Insulate correctly. Use a vented, lockable enclosure with insulation panels or a removable thermal blanket that keeps components above freezing while allowing airflow.

• Heat tape with GFCI. In higher-risk microclimates, our Backflow Testing Los Angeles experts recommend UL-listed heat cable on exposed piping (not on relief openings), with GFCI protection and a thermostat.

• Eliminate wind exposure. Wind chill drives freeze-ups; use wind barriers without blocking drainage or access.

If Your Backflow Preventer Was Submerged During a Flood

Submersion introduces silt, debris, and possibly sewage into the assembly and downstream plumbing. Treat it as contamination until proven clean.Immediate actions:

• Isolate the device. Shut upstream and downstream valves. If the assembly supplies fire protection, notify your fire alarm/monitoring vendor and authority having jurisdiction before taking it offline.

• Do not attempt to operate. Turning handles can draw contaminants into moving parts and scratch sealing surfaces.

• Wait until waters recede, then assess. Note the waterline, debris around the relief port (RPZ), and any visible damage.

Cleanup, repair, and testing:

• Disassemble and disinfect. Our Backflow Testing Los Angeles experts recommend full disassembly, cleaning, and sanitizing of checks, relief valve, and internal cavities with an appropriate disinfectant solution (per manufacturer and purveyor guidance). Replace rubber parts and springs.

• Flush upstream and downstream piping. Clear silt and biofilm before reassembly and testing to prevent recontamination or fouling.

• Evaluate enclosures and drainage. Clear drains, remove trapped silt, and restore ventilation. Replace any waterlogged insulation.

• Test to certification standards. After reassembly, a certified field test verifies check differential pressures and proper relief valve operation under load.

• Replace if compromised. Bent stems, scored seats, or corroded castings from dirty floodwater may justify replacement over repeated repairs.

Special note for RPZs: The relief valve is designed to discharge; if submerged, contaminants likely entered the relief zone. Many purveyors require at least a rebuild and test, and in severe events replacement may be recommended for reliability.

Our Backflow Testing Los Angeles experts recommend treating any submerged RPZ as out-of-service until cleaned, rebuilt, and tested.

Repair vs. Replace: How to Decide

• Replace when:

  • The body/cover is cracked or warped.

  • Seats are deeply scored or pitted and seat kits won’t restore seal.

  • Repeated tests fail after a complete rebuild.

  • Corrosion or contamination is extensive, or parts are obsolete.

• Repair/rebuild when:

  • Damage is limited to rubber parts, springs, test cocks, or ball valves.

  • No cracks in castings and seat surfaces can be restored.

  • The device is a current, listed model with parts readily available.

Our Backflow Testing Los Angeles experts recommend factoring lifecycle cost: a full rebuild plus repeat service calls can exceed the price of a new, listed assembly—especially on older models.

Compliance and Documentation (Los Angeles Essentials)

• Annual testing (minimum). Most LA-area purveyors require annual testing and immediate retesting after repair, freeze damage, or flooding.

• Keep records. Save photos, test reports, repair invoices, and serial numbers. This helps with insurance claims and purveyor requests.

• Permits/notifications. Relocations, enclosure additions, or fire-line work may trigger permits or AHJ notifications. When in doubt, ask—we coordinate with local purveyors daily.

Atlas Backflow Services stays current with regional specifications so your restored device passes inspection the first time.

Prevent Future Freeze and Flood Damage

• Upgrade the enclosure. Use a lockable, ventilated, and insulated enclosure with clearances for testing. For flood-prone areas, choose elevated bases with open drains.

• Improve site grading and drainage. Add French drains or trench drains to move stormwater away from the device. Keep the relief valve on RPZs clear of splash-back paths.

• Raise at-risk assemblies. Our Backflow Testing Los Angeles experts recommend elevating RPZs above anticipated high-water marks; avoid pits or vaults for RPZs.

• Protect valves and test cocks. Install freeze-resistant ball valves and keep threaded caps on test cocks to reduce intrusion.

• Schedule seasonal checks. Pre-storm and pre-winter inspections catch loose insulation, clogged drains, and failing heat tape before a weather event.

Quick Action Checklist

• Shut upstream/downstream valves; isolate the device

• No operating or cycling until inspected

• Photograph condition and surroundings

• For freezes: thaw slowly, no open flame; schedule test

• For floods: disassemble, disinfect, rebuild, flush lines, then test

• Repair/replace based on findings and part availability

• Update documentation; submit test results to your purveyor

• Add prevention: insulation, heat tape (GFCI), elevation, drainage

Call Atlas Backflow Services

If your backflow preventer just froze or was underwater, time matters. Atlas Backflow Services can inspect, rebuild, flush, and certify your assembly—often in a single coordinated visit.

From emergency isolation to final paperwork, our Backflow Testing Los Angeles experts recommend a practical, code-aligned plan that restores service and reduces future risk.Reach out today to schedule priority service and a prevention audit.

We’ll help you protect your water, your property, and your compliance—no guesswork, no delays.