Quick answer: To winterize a sprinkler system, shut off the water, drain the pipes and blow the remaining water out with a compressor, one zone at a time. Keep the air pressure regulated at about 30–50 psi and use high air volume, not high pressure. A shop compressor is often too small. If you are unsure, or your system has a backflow preventer or a well, hire a licensed irrigation technician; the cost is small compared with cracked pipes.
Before You Start: Know Your System
- Pipe type: PVC main lines tolerate more pressure than poly (flexible) pipe. Poly is commonly limited to about 50 psi.
- Head rating: sprinkler heads are rated for normal water pressure (often 30–100 psi); excess air can blow nozzles off.
- Backflow preventer: if your system has one, check the manufacturer’s steps first, and consider a technician.
- Controller: many smart controllers have a “winterize” or “manual valve” mode that runs each zone for you. For example, see our Rachio 3 review and Rain Bird ST8i review.
When to Winterize
Blow out the system before the first hard freeze, when nighttime temperatures stay near or below freezing. Many northern areas do this in October or early November. Warm southern climates can wait longer, and some do not need a full blowout at all. Frozen water expands and splits pipes and valves, and the damage often shows up only in spring.
Step by Step: The Blowout
- Turn off the water supply to the irrigation valve, and turn off the controller.
- Open the drain at the main line, if your system has one, to release standing water.
- Connect the compressor to the blowout port (or the mainline fitting) through a regulator set at about 30–50 psi.
- Open one zone at a time with the controller’s manual test function, starting with the zone farthest from the valves.
- Watch the heads. Let the zone run until the heads spray only air or stop spraying, then move to the next zone. Keep runs short; stop when the water is gone rather than running air for a long time.
- Repeat for every zone and leave the drain valves open for the winter.
Why Volume Matters More Than Pressure
Blowing out a system is about moving a large amount of air to push water out of the pipes, not about high pressure. Michigan State University’s extension article makes this point, and it explains why a small shop compressor can run out of air before a long zone is clear. Pick a compressor rated in cubic feet per minute (CFM) that is large enough for your system, or rent one from a tool shop. Use the regulator, not the compressor’s dial alone, to set the pressure.
Planning your spring setup? See the best sprinkler controllers before you reinstall.
Common Mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Too much pressure | Nozzles blow out; pipes or fittings crack | Use a regulator at 30–50 psi |
| Running one zone too long | Heads overheat or pipe joints stress | Short runs, then move on |
| Skipping the drain valves | Water trapped in low spots freezes | Open drains and leave them open |
| Turning off the controller only | Water stays in the lines | Blow out every zone |
| Hand-blowing from a garden hose | Does not clear the lines and can damage valves | Use a compressor and regulator |
Spring Startup
- Close the drains and turn the water supply back on slowly.
- Check each zone for leaks at the heads and valves.
- Run each zone manually and watch the spray pattern.
- Reset the controller’s schedule for the season.
Need a new controller or heads before spring? See our irrigation ideas for your garden and Orbit Yard Enforcer review.
To plan the whole system before the cold season, see our complete sprinkler buying guide.
Frequently Asked Questions
Can I winterize a sprinkler system myself?
Yes, if you have a compressor with enough air volume and a regulator. If you have a backflow preventer, a well or a complex layout, consider a technician.
What psi should I use to blow out sprinklers?
Most residential guidance keeps blowout pressure at or below about 50 psi, and many use 30–50 psi with a high-volume compressor. Check your pipe and head ratings.
Can I just turn off the water and skip the blowout?
Not reliably. Water left in low spots and valves can freeze and crack them, even when the controller is off.
Do I need to winterize in Florida or Texas?
In mild winters, often not. Watch the forecast: if freezes are expected, winterize before the first hard freeze.
The Bottom Line
Shut off the water, drain the system and blow each zone out with a high-volume compressor and a regulator at about 30–50 psi, before the first hard freeze. If the system is complex, a technician is cheaper than a repair in spring. For a yard that’s ready next season, see our watering guide.
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