Yardtally is reader-supported. Some links on this page are affiliate links. As an Amazon Associate, Yardtally earns from qualifying purchases. See our Affiliate Disclosure.
Learning how to winterize your sprinkler system correctly can save you hundreds in spring repairs — cracked pipes and broken heads are almost always preventable with one afternoon of work in October. Here’s the full process, whether you’re blowing out the lines yourself or using the manual drain method.
How to Winterize Your Sprinkler System: Two Methods
Water expands when it freezes. Any water left sitting in your irrigation pipes, valves, or heads when temperatures drop below 32°F can crack PVC pipes, split poly tubing, damage backflow preventers, and destroy sprinkler heads. A single cracked backflow preventer can cost $200–$500 to repair. The winterization process costs almost nothing by comparison.
When to Winterize
Winterize before your first hard freeze — a night where temps drop below 32°F for several hours. In Indiana and most of the Midwest, that’s typically mid-October. In the Northern Plains and upper Midwest, late September. In the transition zone and South, November. Don’t wait until the last minute — ground freezes faster than most people expect once cold snaps start.
Not sure when to make your final watering pass before winterizing? Our guide on when to stop watering your lawn in fall covers the cutoff timing by region and grass type.
There are two ways to winterize: the blow-out method (most thorough, works for any system) and the manual or automatic drain method (works only for systems designed with drain valves). Most residential in-ground systems use the blow-out method.
Whether you’re doing this for the first time or just need a refresher, knowing how to winterize your sprinkler system before temperatures drop is one of the easiest ways to protect a major yard investment.
Method 1 — The Blow-Out Method (Recommended)
This is what I researched and what most irrigation professionals use. It removes water from every zone completely by forcing compressed air through the lines.
What You Need
You need an air compressor with at least 20 CFM (cubic feet per minute) of airflow — not just high PSI. A standard small pancake compressor like the Porter-Cable 6-gallon pancake compressor works for systems with 1–2 zones but may need extra passes on larger systems. For systems with 3+ zones, renting a higher-CFM compressor from Home Depot or Menards ($40–$60/day) is a better option.
You also need a sprinkler blow-out adapter a quick-connect fitting that threads onto your system’s blow-out port and connects to your compressor hose. Most systems have a blow-out port near the backflow preventer. If yours doesn’t, a plumber can add one for under $50.
Step-by-Step Blow-Out Process
- Disable the irrigation controller — set it to “rain” or “off” mode so it doesn’t try to run a zone during the process.
- Locate the blow-out port on your system — usually a brass cap near the backflow preventer or main shutoff. Remove the cap and attach the blow-out adapter.
- Connect your compressor to the adapter. Do not exceed 50 PSI for PVC pipe systems or 80 PSI for poly pipe systems. Higher pressure can damage heads and fittings.
- Manually activate the farthest zone from the compressor using your controller or the manual solenoid on each valve. Run the compressor until the heads stop spraying water and only mist or air is coming out — usually 2–3 minutes per zone.
- Move zone by zone from farthest to closest, working back toward the compressor. Each zone gets 2–3 passes until no water comes out.
- Never run the compressor with no zone open — pressure with nowhere to go can damage the system. Always have a zone activated before running air through.
- Once all zones are clear, remove the adapter, replace the blow-out port cap, and shut off the main water supply to the irrigation system at the backflow preventer or dedicated shutoff.
Protect the Backflow Preventer
The backflow preventer sits above ground and is the most vulnerable part of your system to freeze damage. After blowing out the lines, wrap it with foam pipe insulation and secure it with tape. This adds enough thermal protection to handle brief temperature dips even if you cut it close on timing.
Method 2 — Manual Drain Method
Some systems are installed with manual drain valves at the low points of each zone. If your system has these, winterizing is simpler: shut off the main irrigation water supply, open each manual drain valve to let water run out by gravity, and leave the valves open until spring. Check your system’s installation manual or ask your irrigation installer whether your system has drain valves.
Method 3 — Automatic Drain Method
Automatic drain valves open on their own when pressure drops below a certain threshold. If your system has these, simply shut off the main water supply and briefly activate each zone to release pressure — the automatic drains do the rest. Again, check your installation manual to confirm your system type before assuming this method applies.
Don’t Forget the Controller
After winterizing, set your irrigation controller to its off or rain mode for the season. Some controllers have a dedicated “seasonal shutdown” setting. If your controller is mounted outdoors, check whether it’s rated for freezing temperatures — some are not and should be brought inside or covered.
What Happens If You Skip Winterization
The most common failure is a cracked backflow preventer — they’re brass or bronze, they sit above ground, and they’re expensive to replace. Next most common is split poly tubing underground, which requires digging up sections of your yard to repair in spring. Sprinkler heads can also crack and need replacing. None of these failures are dramatic — they just show up quietly in spring when you turn the system back on and find soggy spots, dead zones, or a geyser in the corner of your yard.
Spring Startup Checklist
When you turn the system back on in spring, do a slow startup: open the main water supply gradually (never fast — water hammer can damage pipes), then walk each zone while it runs to check for broken heads, misaligned sprays, and leaks. Catching damage early in spring means a simple fix rather than a mid-summer irrigation failure.