Do I Need to Shut Off or Drain My Backflow Device Seasonally—and How?
- bill57931
- 2 days ago
- 5 min read
Los Angeles has mild winters, but microclimates, desert winds, and occasional cold snaps can still cause freeze damage—especially in the Valley, foothills, and higher elevations. Meanwhile, irrigation systems often go dormant from late fall to early spring.
So, do you need to shut off or drain your backflow device seasonally, and how should you do it correctly? Here’s what Atlas Backflow Services and our Backflow Testing Los Angeles experts recommend to protect your assemblies, stay compliant, and simplify spring start-up.
Quick Answer: Who Should Winterize?
Irrigation-only systems (PVB/SVB or RPZ on sprinklers): Yes. Shutting off and draining for the off-season prevents freeze damage and nuisance leaks.
Properties in frost-prone microclimates: Consider seasonal draining or upgraded protection.
Vacant buildings or seasonal operations: Yes—winterize to avoid unnoticed failures.
Domestic and fire service assemblies in use year-round: Typically no shutoff. Keep them active, protected, and tested annually.
When in doubt, our Backflow Testing Los Angeles experts recommend a quick site assessment to balance risk, convenience, and code requirements.
Important Compliance Note
Annual testing is required by most LA-area purveyors. After any repair or relocation, re-testing is required.
Do not obstruct relief valves (especially on RPZs). Never cap, plug, or seal any relief opening or vent.
Follow manufacturer instructions and local purveyor rules. If you’re not sure, we can confirm requirements for your address.
Seasonal Shutoff vs. Full Drain-Down
Seasonal shutoff means closing the water supply to the device and isolating downstream use.
Drain-down means removing water from the assembly and nearby piping so trapped water can’t freeze and expand.
In LA, seasonal shutoff plus partial draining is often enough for irrigation assemblies. For colder zones or exposed locations, full drain-down (and optional blow-out for irrigation lines) offers better protection.
How to Winterize by Device Type
Always wear eye protection and proceed slowly. If you’re not comfortable performing these steps, our Backflow Testing Los Angeles experts recommend scheduling a professional winterization to avoid damage.
Pressure Vacuum Breaker (PVB) or Spill-Resistant Vacuum Breaker (SVB) – Common on Irrigation
Shut off upstream (inlet) valve.
Open downstream isolation valve (if present) to relieve pressure, then return it to the closed position.
Open all test cocks to drain trapped water. Leave them at a 45-degree angle for the winter so moisture can escape.
On PVB/SVB bonnets, the air inlet opens automatically as pressure drops; do not tape, cap, or seal it.
If you have an irrigation system, consider a professional line blow-out. This clears lateral lines, heads, and low points where water sits.
Add a ventilated, insulated enclosure. Do not wrap so tightly that vents are blocked.
Reduced Pressure Zone Assembly (RPZ) – Irrigation or Domestic
Shut off upstream valve, then close the downstream valve to isolate the system.
Open all test cocks from lowest to highest to drain. The relief valve will open as pressure bleeds off; ensure the relief discharge path is unobstructed.
Do not plug the relief port or enclose the RPZ in a sealed box. RPZs must be above grade with unobstructed drainage.
In colder pockets, use a lockable, ventilated, insulated enclosure. For exposed installs, our Backflow Testing Los Angeles experts recommend heat cable on adjacent piping (never on the relief body), GFCI-protected and thermostat-controlled.
Double Check Valve Assembly (DCVA) / Double Check Detector Assembly (DCDA) – Domestic or Fire
Shut off upstream, then open a low downstream drain or hose bib to relieve pressure.
Open test cocks to let trapped water escape from the body.
For vault installations, pump out standing water and confirm the sump/drain functions. DCs are not designed to be submerged; recurring water in vaults should be addressed before winter.
Reinstall protective caps on test cocks after draining to keep debris out.
Extra Protection in LA Microclimates
Insulated, ventilated enclosures: Prevent wind chill while allowing moisture to escape.
Heat tape (where needed): Apply only to straight piping, never across the RPZ relief or bonnet vents. Use GFCI circuits and a thermostat. Our Backflow Testing Los Angeles experts recommend periodic function checks before cold nights.
Elevation and drainage: Keep RPZs above grade with a clear discharge path; add gravel bases or drains to prevent pooling.
Common Mistakes to Avoid
Plugging or sealing an RPZ relief port. This is unsafe and a code violation.
Wrapping an assembly in plastic bags or unvented covers. Traps moisture, accelerates corrosion, and can freeze faster.
Leaving valves half-open. Either fully open or fully closed per the steps above. Half-open valves can trap water and fail.
Skipping irrigation blow-out in known freeze pockets. Trapped lateral water will rupture fittings and sprinkler heads.
Forgetting to re-test after repairs. If any components are replaced or rebuilt, re-testing is required.
Our Backflow Testing Los Angeles experts recommend a quick photo log of valve positions and open test cocks after winterization—handy for spring start-up.
Spring Start-Up: How to Reactivate Safely
Inspect visually: Look for damage, missing caps, vandalism, or nesting inside enclosures.
Close all test cocks and ensure drain points are shut.
Open downstream valve first to avoid sudden backpressure, then slowly crack the upstream valve to fill the assembly gently. Air and water will equalize without hammer.
Check for leaks at test cocks, bonnet covers, and shutoffs.
Schedule annual testing to maintain compliance and catch any winter-related wear, especially on rubber checks and springs.
For irrigation systems, restore controller programs and walk the zones to spot breaks or stuck heads.
If you hear chattering, see discharge from an RPZ relief, or notice low pressure, our Backflow Testing Los Angeles experts recommend stopping and calling for a certified test and repair before placing the system into full service.
Seasonal Checklist (LA Edition)
Decide if your device needs winterization:
Irrigation or vacant property: Yes
Year-round domestic/fire: Usually no, but ensure protection and access
Shut off upstream; relieve pressure downstream
Open test cocks to drain; leave at 45 degrees (irrigation)
Ensure RPZ relief path is clear; never capped
Add insulated, ventilated enclosure; consider heat tape on piping (GFCI)
For irrigation: blow out lines in freeze-prone areas
Document positions and take photos for spring
In spring: close test cocks, open valves slowly, check leaks, schedule annual test
Why Partner with Atlas Backflow Services
Seasonal protection shouldn’t be guesswork. Atlas Backflow Services can winterize, blow out irrigation lines, restore in spring, test for compliance, and upgrade enclosures and drainage where needed.
From device-specific procedures to purveyor paperwork, our Backflow Testing Los Angeles experts recommend a streamlined plan that fits your property, budget, and local code.Have questions about your address or device type?
Contact Atlas Backflow Services for a quick assessment. We’ll help you decide whether to shut off, drain, or upgrade protection—and we’ll make sure your assembly is ready for whatever LA weather brings next.
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