How do I winterize my irrigation backflow preventer properly?
- bill57931
- Oct 15
- 5 min read
Shut off the irrigation supply, relieve pressure, drain the assembly, set the ball valves at 45 degrees, open test cocks, and insulate with a breathable backflow cover. In Orange County’s mild climate, you may only need this during cold snaps.
After any winterization or freeze event, schedule a certified test before the spring startup. For a smooth, compliant process, our backflow maintenance Orange County experts recommend letting a certified technician verify operation and file required test reports. Atlas Backflow Services can handle it end-to-end.
Why winterize in Orange County?
Orange County doesn’t see long winters, but sudden overnight freezes do happen—especially inland and in higher elevations. A few hours below 32°F can crack a Pressure Vacuum Breaker (PVB) or Reduced Pressure (RP) assembly, leading to leaks, fines for water waste, and expensive replacements.
Since irrigation assemblies are typically above ground and exposed, small steps now prevent big costs later. That’s why our backflow maintenance Orange County experts recommend a quick winterization protocol any time a freeze watch is issued.
Know your device: PVB vs. RP
PVB (Pressure Vacuum Breaker): Very common on irrigation systems. Vulnerable at the bonnet, poppet, and test cocks.
RP (Reduced Pressure Principle Assembly): Used when there’s chemical injection or higher hazard. The relief valve is especially freeze-sensitive.
Both types can be protected with the same basic approach: isolate, drain, relieve pressure, and insulate.
What you’ll need
Flathead screwdriver or test cock key
Adjustable wrench (if needed for access)
Insulated, weatherproof backflow cover or enclosure (UV-resistant, breathable)
Optional: UL-listed heat tape with thermostat (usually not necessary in Orange County)
Clean rags or towels
Marker or tag to note winterized status
Our backflow maintenance Orange County experts recommend purpose-built insulated covers rather than plastic bags or household blankets, which can trap condensation and accelerate corrosion.
Step-by-step: Winterize a PVB (most irrigation setups)
Turn off the irrigation water supply
Locate the upstream shutoff valve feeding the backflow assembly. Rotate the handle to OFF. This isolates the device from house pressure.
Shut down irrigation controller
Place your irrigation timer in OFF or Rain mode. This prevents accidental pressurization during a cold snap.
Relieve internal pressure
Slowly open a downstream hose bib or remove a sprinkler cap to release trapped water.
On the PVB, crack open the test cocks (small slotted screws) 1–2 turns to let air in and water out. You should hear a small hiss.
Drain the assembly
With test cocks open, rotate both shutoff ball valves (inlet and outlet) to about 45 degrees—halfway between fully open and fully closed.
This position helps prevent valve body cracking and allows residual water to expand safely if temperatures dip.
Protect exposed components
Loosely wrap the body with a breathable insulated cover sized for your assembly. Ensure test cocks remain slightly open and the relief air vent (PVB bonnet) is not sealed airtight.
Do not use plastic sheeting, trash bags, or unvented wraps; moisture can build up and cause corrosion.
Tag it
Place a small tag or note at the controller or on the assembly: “Winterized—do not operate until de-winterized.”
Our backflow maintenance Orange County experts recommend checking the cover after wind or rain to ensure it’s still secure and dry.
Step-by-step: Winterize an RP assembly (if your irrigation uses an RP)
Isolate at the upstream shutoff.
Open a downstream point to relieve pressure.
Open all test cocks 1–2 turns.
Leave inlet and outlet ball valves at 45 degrees.
Confirm the relief valve discharge path is clear; don’t seal it inside an airtight bag.
Install a breathable insulated enclosure with access panels.
RPs can trap water in the relief valve body; the 45-degree valve position and open test cocks help purge water and reduce risk. In areas expecting extended freeze, consider an enclosure with a UL-listed heater and thermostat, installed by a qualified electrician. In Orange County, insulation is typically sufficient.
Optional: Blow out irrigation lines
While not always necessary in our climate, low-lying or shaded zones can freeze. If you choose to blow out lines:
Use an air compressor with a regulator.
Keep pressures conservative: typically 40–60 PSI for residential PVC/PE zones, lower for drip.
Blow out each zone briefly until mist clears; do not run continuous high-pressure air—it can damage heads and drip fittings.
If you’re unsure, our backflow maintenance Orange County experts recommend leaving blowouts to a professional, especially on mixed-material systems.
Common mistakes to avoid
Fully closing ball valves after draining: This can trap water in the ball cavity and cause cracking. Keep them at 45 degrees.
Wrapping in plastic or non-breathable materials: Traps moisture and corrodes brass/steel components.
Using heat lamps or open-space heaters: Fire hazard and uneven heating.
Forgetting to open test cocks: Prevents proper drainage and air entry.
Skipping spring testing: After any winterization or suspected freeze, a certified test ensures the assembly actually protects your water.
Our backflow maintenance Orange County experts recommend a quick visual check after any cold night: look for dripping, distorted bonnets, or cracked housings.
Spring de-winterization (and compliance)
When warmer weather returns or after the cold snap passes:
Remove the insulated cover and inspect for damage or leaks.
Close test cocks gently.
Open the upstream shutoff slowly to repressurize.
Return ball valves to fully open.
Run irrigation zones and observe for any leaks or abnormal discharge.
Schedule a certified backflow test—especially if any freeze occurred or if you performed repairs.
In many Orange County jurisdictions, annual backflow testing is required. Atlas Backflow Services performs the certified test, provides your report, and submits it to your water purveyor through the correct portal. It’s the simplest way to close the compliance loop.
Special considerations for Orange County properties
Coastal vs. inland: Inland valleys see more freeze risk than coastal neighborhoods. Watch microclimates—canyons and shaded yards freeze first.
HOA and commercial sites: Multiple devices may require coordinated winterization, tagging, and documentation. We can inventory all assemblies and implement a site-wide plan.
Enclosures: Attractive, lockable, insulated enclosures protect from both weather and vandalism—ideal for streetside installations.
Our backflow maintenance Orange County experts recommend installing a permanent insulated enclosure if your assembly has frozen before or sits in a wind corridor.
FAQs
Do I have to winterize every year in Orange County?
Not always. But when a freeze watch is issued, take these steps. It’s quick insurance against damage.
Can I just throw a blanket over it?
Avoid household blankets and plastic. Use a breathable, insulated cover sized for your assembly.
My PVB drips after a freeze. Is it ruined?
Possibly the bonnet or internals cracked. Shut off water and call a pro. We can rebuild with approved parts and perform a certified test.
Do I need a certified test after winter?
It’s highly recommended—and often required annually by your water purveyor. We test, document, and submit on your behalf.
Conclusion
Proper winterization takes minutes: isolate, drain, open test cocks, set valves at 45 degrees, and cover with breathable insulation. In our region, that’s usually enough to ride out cold snaps. For safety and compliance, our backflow maintenance Orange County experts recommend a certified test after winter and any time you suspect freeze damage.
Atlas Backflow Services can winterize your irrigation backflow preventer, perform repairs if needed, test with calibrated equipment, and submit your passing report to the water purveyor. Contact us today to schedule preventive service or set up an automatic cold-snap readiness plan.
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