How to winterize a sprinkler (irrigation) system
To winterize a sprinkler or irrigation system, shut off the irrigation water supply, then get the water out of the lines before the first freeze: open the manual drain valves, let automatic drains work, or blow the lines out with compressed air one zone at a time. Protect the backflow preventer and set the controller to "off" or "rain" mode for the winter.
How to winterize a sprinkler (irrigation) system
Checklist
- Shut off the main irrigation valve (often in the basement or crawl space)Before the first freeze
- Turn the controller to off / rain modeSame day
- Drain the lines: manual drains, automatic drains, or blow-outSame day
- Open the backflow preventer test cocks and leave ball valves half-openAfter draining
- Insulate the backflow preventer and any above-ground pipeAfter draining
- Bring drip-system timers, filters, and pressure regulators indoorsAfter draining
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Three ways to drain the lines
Manual drain: open the drain valves at the low points of each zone and let the water run out. Automatic drain: these valves open on their own when pressure drops; run each zone briefly after shutting off the supply so they trigger. Blow-out: push the water out with compressed air, zone by zone.
Start with the simple methods. Use the blow-out method when your system has no drains or you live where the ground freezes deep.
If you blow it out yourself
You need a compressor that moves a lot of air; a small shop compressor usually is not enough. Close the backflow isolation valves first so air does not go through the backflow device. Open one zone at a time and run air until only mist comes from the heads, then do a second short pass.
Keep pressure low and never run air through a zone with all its valves closed. Sources disagree on the exact number, so use your system manufacturer's limit. Wear eye protection. If you are not sure, this is a common job to hire out, and booking early in the fall is easier.
What you'll need
- Sprinkler blow-out adapterConnects a compressor to the system's blow-out port
- Backflow preventer insulation coverKeeps the backflow device from freezing
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Questions
When should I winterize my sprinkler system?
Before the first hard freeze in your area. For most of the northern U.S. that means October to early November.
Do I need to blow out my sprinklers if I have automatic drains?
Not always. Automatic drains handle many systems in milder climates. In places where the ground freezes deep, or if water collects in low spots, a blow-out is the safer choice.
What PSI should I use to blow out sprinklers?
Use the limit from your system's manufacturer. Published advice ranges widely, and too much pressure can damage pipes and heads.
Sources
- HGTV — How to Winterize Sprinklers, Hoses and Irrigation Systems
- Landscape Management — Step by step: how to winterize an irrigation system
Related guides
General guidance for typical homes. Follow your equipment manufacturer's instructions and local codes, and hire a pro for anything you're not comfortable doing.