How often should you winterize your sprinkler system?
Updated July 2026
Winterize your sprinkler system once every fall, before the first hard freeze. In most of the freeze-prone US that means booking the blowout for October, and September in the coldest zones. The system's most fragile parts sit above ground or just below the frost line: the backflow preventer, the manifold, and the heads all hold water, and water that freezes in them cracks brass and splits PVC quietly; you find out in April, when the first zone turns the yard into a fountain. A pro blowout runs $75–150; irrigation companies book out fast once the first frost hits the forecast, so schedule early.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Hard-freeze climate (ground freezes) | Blowout every fall, no exceptions | Compressed-air blowout is the only method that reliably empties buried lines |
| Borderline climate (occasional light freezes) | Drain the backflow and above-ground parts | The exposed brass is what cracks in a surprise cold snap |
| System has manual/automatic drain valves | Manual-drain method possible | Only if the system was designed for it; low points still trap water |
| First freeze forecast and you’re not done | Insulate the backflow preventer tonight | Foam covers or towels-and-a-bag buy a night or two, not a season |
| Spring restart | Slow re-pressurization, walk every zone | Opening the main valve fast hammers winter-brittle fittings |
| Drip irrigation | Drain and cap the same fall date | Thin poly tubing and emitters split just as readily |
The cost of skipping it
What skipping it costs: the freeze does its damage invisibly and presents the bill in spring. The classic casualty list: a cracked backflow preventer ($150–500 replaced; the brass body splits and it's the one component code requires), split manifolds and fittings ($100–400 plus digging), and cracked heads and risers ($20–50 each, and they rarely crack alone). A bad year with a split main line means trenching. Against that: $75–150 for the blowout, or an hour of DIY draining in mild climates. One missed fall routinely costs 3–10 winterizations' worth of repairs.
How to do it (Pro blowout · $75–150 · book it by early October)
- Book the blowout when nights first dip toward the 30s: after the lawn’s last real watering need, before the first hard freeze.
- Or the pro’s process, if DIY-curious: shut the irrigation water supply, open the drains, and blow each zone with compressed air until heads run mist, but note the air volume matters more than pressure (rental tow-behind compressors, not pancake compressors, and never over ~80 PSI on poly pipe).
- Either way: shut off the controller (or set to "rain/off" so the programming survives), and leave the backflow preventer’s test cocks and ball valves at 45° so trapped water has room to expand.
- Insulate what stays wet and exposed: a foam cover on the backflow preventer costs $15 and covers the borderline nights.
- Log the date: the matching spring task is a slow re-pressurization and a walk of every zone looking for the winter’s damage.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing the fall blowout booking schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
Can I winterize the sprinklers myself without a compressor?
Only if your system was built for manual draining: valves at the low points of each zone plus automatic drain valves at the heads. Open everything, drain the backflow, done. It works in milder climates and well-designed systems. In hard-freeze country, buried low spots still hold water that only moving air removes, which is why the blowout is the standard. A small home compressor genuinely can't move enough air volume; that's the part DIYers learn the expensive way.
When exactly is “before the first hard freeze”?
You're protecting against a night in the mid-20s°F or lower; light overnight frosts won't crack buried pipe. Watch the 10-day forecast from late September on (earlier in mountain and northern-plains zones) and get the blowout done ahead of the first forecast hard freeze rather than after a warning. The pros' calendars are the real constraint: by the time the freeze warning airs, everyone's calling.
What if a surprise freeze hits before my blowout appointment?
Triage the exposed parts: shut off the irrigation supply, open the backflow preventer's drain/test cocks so it can empty, and wrap it: foam cover, or towels inside a plastic bag in a pinch. The buried lines have soil insulation and survive a brief first frost far better than the above-ground brass does. Then keep the appointment.