How to Winterize Your Sprinkler System in 2026

Why Winterizing Your Sprinkler System Matters

Freezing water expands by 9 percent. Even a small amount of trapped water in your irrigation lines can crack pipes, split valves, and destroy backflow preventers. Repair costs easily exceed $500 to $2,000. A proper winterization takes 1 to 2 hours and costs almost nothing.

When to Shut Down Your System

The rule of thumb: complete winterization before the first hard freeze in your area. Check your local frost dates. In northern zones (3 to 5), aim for mid-October. Southern zones (7 to 9) can wait until late November or early December.

Signs It Is Time to Winterize

• Overnight temperatures consistently drop below 40 F
• Your local weather service predicts a frost warning
• Grass growth has slowed or stopped

Step 1: Shut Off the Water Supply

Locate the main shut-off valve for your irrigation system. This is typically found in the basement, crawlspace, or an outdoor valve box. Turn the valve handle 90 degrees to close it. If you have a separate backflow preventer, close both the supply and return valves.

Step 2: Drain the System

There are three drainage methods. Use the one that matches your system design:

Manual Drain Method

Open all manual drain valves located at low points in the system. Allow water to flow out until it stops. This works best on flat properties where the mainline slopes downward.

Automatic Drain Method

Systems with automatic drain valves will self-drain when water pressure drops below 5 psi. Simply shut off the water and activate each zone briefly to release pressure.

Compressed Air Blowout (Recommended)

This is the most thorough method and is required for systems without drain valves. Rent an air compressor rated at 80 to 100 CFM. Connect it to the system test port. Blow out each zone one at a time. Keep air pressure below 80 psi for PVC pipe and 50 psi for polyethylene pipe.

Step 3: Protect the Backflow Preventer

The backflow preventer is the most freeze-sensitive component. If it is above ground:

• Wrap it with insulated foam covers or towels
• Secure with waterproof tape or plastic wrap
• Alternatively, remove it entirely and store indoors

Step 4: Insulate Above-Ground Components

Valve boxes, above-ground piping, and the main shut-off valve should all be insulated. Use foam pipe insulation or fiberglass wrap. Secure with zip ties or tape to prevent wind from blowing it away.

Step 5: Turn Off the Controller

Set your irrigation controller to "off" or "rain mode." Some homeowners prefer to remove the batteries entirely to prevent corrosion over the winter months. Smart controllers can be left powered but set to standby.

Common Mistakes to Avoid

• Using too much air pressure: Over 80 psi can crack PVC fittings. Use a regulator.
• Skipping zones: Every zone must be blown out. Water trapped in an unused zone will still freeze and cause damage.
• Forgetting the backflow preventer: This is the most commonly damaged component. Never skip insulation.
• Blowing out too fast: Run each zone for 2 to 3 minutes. You will see a fine mist when all water is expelled.

Spring Startup Checklist

When warm weather returns, follow these steps to reactivate your system:

1. Remove all insulation from components
2. Slowly open the main water supply valve
3. Inspect each zone for leaks or damage
4. Reprogram your controller with current watering schedules
5. Run a complete system test before the growing season begins

Pro tip: Keep a written record of your winterization date and any issues discovered. This helps plan next year's maintenance and identifies recurring problem zones.

When to Hire a Professional

Consider calling an irrigation professional if your system is large (8 plus zones), has complex elevation changes, or if you do not own a suitable air compressor. Professional blowout services typically cost $75 to $150 and take about 45 minutes.

Frequently Asked Questions

Do I need to winterize if I live in a warm climate?

If your area never experiences freezing temperatures, a full winterization is not necessary. However, you should still shut off the system during the dry season and inspect components annually.

Can I use a regular shop compressor?

Most shop compressors do not provide enough CFM (cubic feet per minute) for an effective blowout. You need at least 20 CFM for small systems and 80 to 100 CFM for larger installations.

How long does winterization take?

A typical residential system takes 1 to 2 hours. The blowout itself is about 30 to 45 minutes. Adding insulation and controller shutdown takes another 15 to 30 minutes.