How to Winterize Your Lawn Sprinkler System (2026 Guide)

Why Winterizing Your Sprinkler System Matters

Leaving water in your irrigation lines over winter can cause pipes to burst, sprinkler heads to crack, and backflow preventers to fail. A single freeze can cost thousands in repairs.

When to Winterize

Schedule blow-out before the first hard freeze in your area. Most regions need this done between late September and mid-November.

Step 1: Shut Off the Water Supply

Locate the main shutoff valve — usually in a basement, crawl space, or underground box. Turn it clockwise to close. If your system has a backflow preventer, close both valves on either side.

Step 2: Drain the Lines

Open all manual drain valves at low points in the system. Let gravity drain as much water as possible. On sloped properties, open zone valves one at a time to let water run downhill.

Step 3: Blow Out With Compressed Air

Connect an air compressor (minimum 80 CFM at 50-80 PSI) to the system's blow-out port. Run each zone for 2-3 minutes until only mist comes from the sprinkler heads. Never exceed 80 PSI — too much pressure can damage pipes.

Step 4: Protect the Backflow Preventer

Drain the backflow assembly completely. Wrap it with insulated foam covers or towels secured with tape. In harsh climates, consider removing and storing it indoors.

Step 5: Insulate Above-Ground Components

Cover above-ground pipes, valves, and the main shutoff with insulated foam. Secure with duct tape or zip ties to prevent wind from stripping the insulation.

Common Mistakes to Avoid

• Skipping the blow-out and relying on drain valves alone
• Using too high air pressure (over 80 PSI)
• Forgetting to open zone valves during blow-out
• Not insulating the backflow preventer

When to Call a Professional

If you don't own a suitable compressor or your system has more than 8 zones, hire an irrigation professional. Most charge $75-$150 for a full blow-out service.