To winterize a sprinkler system, shut off the irrigation water supply, set the controller to off or rain mode, remove the water from every zone by draining it or blowing it out with compressed air, and protect the backflow preventer. Do it before the first hard freeze, which in much of the northern US means October, not November. Knowing how to winterize sprinkler systems is one part of the whole-home routine to lock in before the cold. Below: the right method, regional timing, seven steps, cost, and how to confirm zero flow.
Blowout vs. Drain: Which Winterizing Method Fits Your System?
Sprinkler system winterization takes one of three forms: a manual drain, an automatic drain, or a compressed-air blowout. The right method depends on how your system was built and how cold your winters get; if you can drain a sprinkler system through drain valves, you can often skip the compressor.
| Method | How it works | Best for | What you need | Watch out for |
|---|---|---|---|---|
| Manual drain | Open low-point drain valves for gravity draining | Systems with manual drain valves | A system map | Low spots that hold water |
| Automatic drain | Low-point valves open when pressure drops after shutoff | Systems with automatic drain valves | Shutoff access | Pipe before the zone valves may need a manual drain |
| Blowout | Compressed air pushes water out through the heads | No drain valves, poly pipe, cold climates | Air compressor with a regulator | Excess pressure; never air through the backflow preventer |
Not sure which you have? Check the installer’s paperwork or look for drain valves in the valve box. Colorado State University Extension favors the air blowout method because drained lines can hold water in low spots, and many pros in the coldest regions agree.
When Should You Winterize a Sprinkler System? Timing by Region
Winterize before the first hard freeze in your area, typically a few weeks before your average first-frost date. NC State Extension defines a hard freeze as air below about 28°F, and several hours that cold is a common rule of thumb for risk to exposed pipe. In much of the northern US, that makes winterizing sprinklers an October job, not a November one, because freezing temperatures can arrive early.
| Region | Example states | Typical window | Notes |
|---|---|---|---|
| Northern Plains, Upper Midwest, Mountain West | Minnesota, North Dakota, Montana, Colorado, Wisconsin | Late September to mid October | Book pros early |
| Northeast, Great Lakes, Pacific Northwest | New York, Michigan, Ohio, Pennsylvania, Washington | Mid October to early November | Higher elevations run earlier |
| Mid-Atlantic, Lower Midwest, central Plains | Virginia, Kentucky, Missouri, Kansas | Late October to mid November | Watch for cold snaps |
| Upper South, southern Plains | Tennessee, Oklahoma, north Texas | November, or before the first forecast freeze | Dates swing year to year |
| Gulf Coast, Florida, Southern California, low desert | Louisiana, Florida, Arizona | Often unnecessary | Drain and insulate the backflow preventer before any forecast freeze |
These windows are typical. Check your local first-frost date in NOAA’s U.S. Climate Normals or with your county extension office. If a surprise freeze comes first, shut off the irrigation supply and insulate the backflow preventer right away, then finish on the next warm day.
Before You Start: Parts to Find, Tools, and Safety
Gather these first.
Parts to find
- The irrigation shutoff valve, where the irrigation line tees off the main supply (basement, crawl space, or valve box)
- The backflow preventer, usually above ground near the house
- The controller, the zone valves, and any manual drain valves
Tools
- A flathead screwdriver or valve key for the backflow test cocks
- Work gloves, plus foam insulation or a backflow cover
- For a blowout, an air compressor with a regulator and hose adapter
Safety
- Wear eye protection during a blowout
- Never stand over a head or valve under air pressure
- Keep your system map handy
If anything ran poorly this summer, find a sprinkler leak now, because a cracked line or leaking valve is easier to repair before the system sits all winter.
How to Winterize a Sprinkler System in 7 Steps
Work through these in order; a short video walkthrough can accompany this list.
- Check for leaks before you shut down. Run each zone once and look for soggy spots, geysers, low pressure, or a valve that will not close. Our guide to irrigation leak detection shows where to look.
- Shut off the water to the irrigation system. Close the irrigation shutoff valve fully.
- Turn the controller off or set it to rain mode. That stops it from running zones on an empty system. Leave it powered if it needs power to keep its program.
- Release pressure and open drain points. Open the backflow test cocks and any manual drain valves.
- Remove the water. Drain it, or blow out each zone (see the sections below).
- Drain and protect the backflow preventer. Drain it and any above-ground pipe, then insulate it (see the backflow section).
- Confirm the system is drained and shut off. Make sure no water is flowing on the irrigation line (see the zero-flow section).
A typical residential system takes about an hour or two to do yourself.
How to Winterize a Sprinkler System Without a Blowout
If your system has drain valves, you can usually winterize your sprinkler system without an air compressor.
Manual drain valves. With the supply off, open the manual drain valves at the ends and low points of each line, plus the test cocks on the backflow preventer. Let the lines empty fully, then close the valves unless your installer or extension service advises leaving them open.
Automatic drain valves. An automatic drain valve opens on its own when pressure drops. Shut off the supply, then run each zone for a few seconds to trigger the valves. The stretch between the shutoff and the zone valves may still need a manual drain or a bleed at a solenoid valve.
The limit: drain methods leave water in any low spot or sag. Colorado State University Extension notes that buried pipe shifts and drained lines cannot be inspected, so many pros in very cold climates still blow out the lines.
How a Sprinkler Blowout Works (and When to Hire It Out)
A sprinkler blowout uses compressed air to push water out of each zone through the heads. It clears more water than draining, but too much air pressure or heat can damage parts, so the rules matter.
- Connect the compressor at the blowout port or a fitting downstream of the backflow preventer, never through it.
- Open one zone at a time and run air until only mist comes from the heads, then move on.
- Keep pressure modest and regulated. Colorado State University Extension gives about 80 psi as the maximum for rigid PVC pipe and about 50 psi for flexible polyethylene pipe.
- Do not keep air running through a dry zone. CSU Extension warns that air moving through dry pipe causes friction and heat that can cause damage, and gear-driven heads are especially exposed.
- Leave a zone valve open while the compressor runs so pressure is never trapped.
Hire it out if you have no large compressor or blowout port, the system is old or fragile, or the property is large.
How Do You Winterize the Backflow Preventer?
Shut off the supply, open the test cocks, drain the device, then insulate it.
- With the irrigation supply off, open the test cocks with a flathead screwdriver.
- Turn the two ball-valve handles partly open. About 45 degrees is the commonly cited setting, and CSU Extension advises leaving the ball valves and test cocks half open for the winter so water drains and ice cannot crack the valve body.
- After draining the lines or blowing them out, wrap the device in an insulated cover or pipe insulation, leaving the vents clear.
This fits the common residential types: pressure vacuum breaker, double check valve, and reduced pressure zone. Some cities require annual backflow testing by a certified tester, so check local rules.
How to Confirm the System Is Drained: Look for Zero Flow
The last step most guides skip is proving the irrigation shutoff is actually holding. A shutoff valve that seeps lets water creep back into the lines you just emptied, and that water can freeze.
- Zero flow: with a flow meter on the irrigation line, the reading after shutdown should be zero.
- Any reading above zero: water is getting past the shutoff, or a valve was left open.
- Next step: close the shutoff firmly, recheck drain points, and repair a valve that will not seal.
Zero flow confirms nothing is moving past the meter; it does not prove the pipes hold no standing water.
Bluebot makes this check simple with a clamp-on meter on the irrigation line. Bluebot meters clamp onto the outside of the pipe using transit-time ultrasonic technology, with no pipe cutting, no water shutoff, and no plumber required, and typical installation takes about 10 minutes using the app. The 50-W (Bluebot Mini) is designed for residential irrigation systems and valve boxes on 3/4-inch and 1-inch pipe, carries an IP68 rating, and detects flow down to 0.3 GPM (1.1 L/min). The 100-W (Bluebot Hero) detects flow down to 0.1 GPM (0.38 L/min). Readings appear in the bluebot Water app. Bluebot detects and alerts; it does not stop a freeze. Its published operating temperature is 32°F to 122°F (0°C to 50°C), so for a meter in an outdoor valve box, ask Bluebot support (1-888-258-4119, CX@bluebot.com) how to handle it over winter.
How Much Does It Cost to Winterize a Sprinkler System?
A professional sprinkler winterization visit typically costs about $60 to $145, according to Lawn Love’s cost guide (updated December 2025), from about $50 for a small drain-only job to about $250 for a large blowout. What moves the price:
- The number of zones and the size of the system
- Your region and the season, since October bookings fill fast
- Bundling with a spring start-up visit
- Add-ons such as backflow insulation or repairs
Doing it yourself is free on a drain-valve system. A blowout needs a compressor that moves enough air; Lawn Love puts air compressor rental at about $30 to $60. Weigh the visit cost against replacing a cracked backflow preventer or a broken zone valve.
Spring Start-Up: How to Turn Your Sprinkler System Back On
Wait until the ground has thawed and the risk of a hard freeze has passed.
- Close any drain valves and the backflow test cocks.
- Return the backflow ball valves to fully open.
- Open the irrigation shutoff slowly, a little at a time, so a rush of water does not cause a pressure surge (water hammer).
- Run each zone and walk the yard, checking heads, spray patterns, and soggy spots.
- Reset the controller program and date.
Spring is when freeze damage shows up. A flow reading that never drops to zero between runs is a sign to look closer, and our guide shows how to catch sprinkler leaks early next spring.
Related Guides
- Doing your own blowout? Our compressor guide shows how to winterize sprinkler system with air compressor equipment, start to finish.
- Spigots need attention the same weekend, so see how to winterize outdoor faucet fixtures too.
Frequently Asked Questions
What happens if you don’t winterize your sprinkler system?
Without irrigation system winterization, water left in the pipes, valves, heads, and backflow preventer can freeze, expand, and crack them. The damage usually stays hidden until spring start-up, when it shows up as geysers, soggy spots, low pressure, or a valve that will not close.
Is it too late to winterize a sprinkler system after the first freeze?
Usually not. Soil insulates buried lines, so a short freeze often reaches only exposed parts such as the backflow preventer and above-ground pipe. Shut off the irrigation supply, insulate the backflow preventer, and finish draining or blowing out a sprinkler system on the next day above freezing. Check the backflow body for cracks before you start.
Is winterizing a Rain Bird or Hunter sprinkler system any different?
Not in the steps. Winterizing a sprinkler system depends on your pipes, drain valves, and backflow preventer rather than the controller brand, so a Rain Bird or Hunter system follows the same shutoff, drain or blowout, and backflow steps. The difference is the controller: check its manual for the off or rain setting and whether it keeps the program without power.
Do I need to winterize my sprinkler system in Texas or other warm states?
It depends on where you live. North Texas and the southern Plains typically need it in November or before the first forecast freeze. Along the Gulf Coast, in Florida, and in the low desert, full winterizing is often unnecessary, but drain and insulate the backflow preventer and exposed pipe whenever a freeze is forecast.
Should backflow valves be left open or closed over winter?
Partly open. After draining, leave the backflow preventer’s ball valves at about a 45 degree angle and the test cocks open, the half-open setting Colorado State University Extension recommends for winter. A fully closed valve can trap water inside the body, where it can freeze and crack the device.