Freezing? Protect Your Vacuum Breaker (Backflow) the Right Way

Outdoor vacuum breakers / backflow preventers on irrigation systems can crack with the first hard freeze. A few quick steps—drain, isolate, insulate—prevent costly spring repairs. Here’s how to winterize a typical PVB (pressure vacuum breaker) or above-grade backflow assembly and what to check at spring start-up.

When to Winterize

• Before nightly lows hit 32°F (0°C) for more than a few hours.
• If a surprise cold snap is coming, do the quick drain steps below and add an insulating cover the same day.

What You’ll Need

• Flat screwdriver or test-cock key
• Adjustable wrench (for unions/bonnets if servicing)
• Insulated backflow cover or enclosure
• Shop towels/bucket

Winterize in Minutes (Most PVB/Above-Grade Assemblies)

Spring Start-Up Checks

• Close test cocks and return shutoff handles to fully open (parallel with pipe).
• Pressurize slowly and inspect for leaks at the bonnet, relief ports, and unions.
• If water vents continuously from the top/relief, inspect/replace bonnet & poppet or check assemblies.

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Code note: Always follow your local plumbing code and manufacturer instructions. Some regions prohibit insulating over test ports without removable access—choose covers that allow service.