Winterizing Your Sprinkler System in Chicago: Blow-Out Method Explained

You're in the Chicago area with a new sprinkler system and need to shut it down for winter. You've heard "blow the lines" but aren't sure what that means.

Why Winterizing Is Critical

Water expands when it freezes with tremendous force—enough to split rocks and burst pipes. If water remains in your system at 32°F, pipes, valves, and fittings will crack.

The Blow-Out Method (Standard for Cold Climates)

1. Shut off main water supply to the irrigation system.
2. Attach air compressor to the system's blow-out port (or via a quick-connect adapter on the backflow preventer).
3. Open one zone at a time.
4. Blow compressed air through the zone until only mist/fog exits heads (no water).
5. Repeat for all zones.
6. Open drain valves (manual or automatic) at low points.
7. Leave valves open (or at 45°) to allow residual condensation to escape.
8. Insulate exposed components (backflow preventer, main shutoff) with foam covers.

Critical Safety Notes

• Pressure: Use 50–80 PSI max. Higher pressure damages pipes/heads.
• Volume: Need 10–25 CFM compressor. Small pancake compressors won't work.
• Never run compressor without a zone open—pressure buildup destroys components.

Alternative: Gravity Drain (Only If System Designed For It)

Some systems have automatic drain valves that open when pressure drops. If yours does, simply shut off water and run the controller through a manual cycle. But in Chicago, blow-out is strongly recommended.

When to Do It

Before first hard freeze (typically late October–early November in Chicago). Don't wait.

Consider Hiring a Pro

If you lack a suitable compressor or experience, a professional blow-out costs $75–$150 and prevents costly spring repairs.