Blow-Out vs. Drain Method

Winterizing an irrigation system removes standing water from pipes and heads before ground freeze. The two primary methods are compressed-air blow-out, which uses a compressor to force water out through the heads, and drain winterization (manual or automatic), which uses gravity or built-in valves to let water exit through low-point drains.

Blow-Out Method

Requires a gas-powered or large-tank compressor (≥ 20 CFM @ 50 PSI)
Fastest method — most zones clear in 2–5 minutes
Works for all pipe materials including PVC and poly
Must be done zone-by-zone; never pressurize the full system at once

Manual Drain Method

Requires manual drain valves installed at the low point of each zone
No compressor needed — suitable for systems designed with correct downhill slope
Must verify each drain valve opens fully and drains completely
Any zone without a low-point drain valve requires blow-out instead

Automatic Drain Method

Automatic drain valves open when system pressure drops below approximately 10 PSI
Minimal tools required — shut off the main, run a head briefly to relieve pressure, and the valves open on their own
Confirm all heads seat correctly after drainage; residual water at a poorly seating head can freeze and crack the body

Pre-Winter Inspection Checklist

Walk all zones and flag any broken or tilted heads before shutdown
Check backflow preventer shutoffs turn fully closed without resistance
Verify controller date/time is correct before programming the shutdown date
Confirm no leaks at valve manifolds or union fittings
Inspect pipe insulation on any above-grade sections (pump houses, risers)

Valve Isolation Steps

Close the main irrigation shutoff (ball valve or gate valve) at the meter or backflow preventer inlet.
Open a downstream hose bib or test cock to bleed residual system pressure.
Close the backflow preventer's inlet shutoff (handle perpendicular to pipe).
Close the backflow preventer's outlet shutoff.
Open both test cocks on the backflow preventer body ¼ turn to relieve trapped water and prevent freeze cracking.
If the system has a manual drain valve at each zone's low point, open each one now and leave open through winter.

When to Call a Professional

If backflow preventer shutoffs are seized or the relief port drips after isolation, schedule a repair before freeze season. See the repair library for winterization equipment specifications and post-winter restart procedures.