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Winterize a sprinkler system by shutting off its water supply, powering down the controller, protecting the backflow preventer, and then removing every bit of water that could freeze inside the pipes — finished one to two weeks before your average first hard freeze. On systems with drain valves at the low points, gravity does the work. On systems without them, the water has to be pushed out with compressed air, one zone at a time, at 50 psi for poly pipe and no more than 80 psi for PVC. That air step is where people damage systems and hurt themselves, so most of this page is about doing it correctly.
We do not install or service irrigation systems; our equipment rankings come from aggregated owner reviews and published specifications, explained in how we rank. The wider subject starts at the watering and irrigation hub.
Do you actually need to winterize where you live?
Not every US yard needs a blowout, and the honest answer depends on how deep your soil freezes rather than on how cold the air gets.
| Region / USDA zone | Buried laterals | What still needs doing |
|---|---|---|
| Zones 9–11: south Florida, Gulf Coast, low-desert AZ/NV, coastal and inland southern CA, deep south TX | Not at risk in a normal winter | Insulate or drain the backflow assembly and exposed risers; disconnect hoses; bring timers and filters indoors |
| Zone 8: coastal Pacific Northwest, much of GA/AL/SC, north FL, central TX | Low risk, occasional hard freeze | Drain what drains by gravity, wrap the backflow device, and shut the system down at the main valve |
| Zone 7: mid-Atlantic, Ohio Valley, TN, OK, northern NM, inland OR/WA | At risk in a cold snap | Full drain; blowout recommended if the system has no low-point drains |
| Zone 6 and colder: Midwest, Northeast, Rockies, Great Plains, mountain West | At real risk every year | Full blowout is standard practice; drain or remove the backflow assembly |
If you are in the first row of that table and someone quotes you for an annual blowout, you are paying for a service your climate does not require. Spend the money on insulating the backflow device instead — in mild regions it is nearly always the only part that ever freezes, because it sits in open air with water standing in the body.
Step 1: Shut down the system properly
- Close the irrigation isolation valve. This is usually a ball valve or gate valve in a basement, crawl space or meter pit, tapped off the house supply upstream of the backflow device. Turn it fully closed, not most of the way.
- Set the controller to off or rain mode. Most modern controllers keep programs in nonvolatile memory, so "off" does not erase your schedule. Older units with a backup battery can lose everything, so photograph the schedule screens before you touch anything. If you are running a smart controller, its app usually has a seasonal shutdown toggle that also stops it sending you "zone did not run" alerts all winter.
- Open the test cocks on the backflow assembly by a quarter turn to relieve pressure and let the body drain. Leave the two ball valves at roughly 45 degrees so no water is trapped between them — a closed valve with water on both sides of the gate is the classic way a brass body cracks.
- Open a manual drain or the lowest drain valve to bleed pressure out of the mainline before you do anything else. Working on a charged line is how fittings become projectiles.
Step 2: Pick the draining method your system was built for
Every residential system uses one of three approaches, and the pipes were sloped (or not) accordingly when they were installed.
| Method | How it works | Honest limitation |
|---|---|---|
| Manual drain | You open a drain valve at each low point and let gravity empty the laterals | Only clears pipe that actually slopes toward the valve; sprinkler bodies still hold a cup of water each |
| Automatic drain | Spring-loaded valves open on their own once line pressure drops below about 10 psi | They clog with grit and fail silently; you have no way to confirm a zone drained |
| Air blowout | Compressed air pushes water out through the heads, zone by zone | Needs real compressor volume; done wrong it splits pipe and breaks heads |
In hard-freeze country the blowout is the default not because the other methods are bad but because they are unverifiable. When you blow out a zone you can see the heads go from spray to mist to dry air, and that is proof.
Step 3: How to blow out sprinkler lines without breaking them
The pressure limits are the whole ballgame. Colorado State University Extension states that ideal pressures fall in the range of 40 to 80 psi, with 80 psi the maximum for rigid PVC pipe and 50 psi for polyethylene pipe. Most residential laterals in the West and Midwest are poly, so 50 psi is the number that governs the majority of yards. A compressor tank sitting at 150 psi connected straight to a lateral will not clear it faster; it will balloon or split it somewhere you will need a shovel to find.
Volume, not pressure, does the actual work. CSU Extension's sizing rule is to divide the zone flow in gallons per minute by 7.5 to get the cubic feet per minute of air required. That is a bare theoretical minimum at the head; in practice, allow several times that at the compressor to account for line losses. A typical residential zone flowing 10 to 15 GPM therefore wants a compressor in the 20 to 50 CFM range, which is a rented towable unit, not something from a home center shelf.
The sequence
- Turn the water off and leave it off. Verify by opening a head or a drain and watching pressure fall to zero.
- Connect downstream of the backflow preventer. Almost every system has a blowout port — a threaded tee with a cap or a quick-coupler — between the backflow assembly and the zone valves. Never push air backward through a backflow device; its internal poppets and rubber seats are not designed for air and you can wreck a several-hundred-dollar assembly in seconds. A brass quick-connect-to-garden-hose blowout adapter (paid link) covers hose-thread ports; a compressor-to-NPT adapter (paid link) covers threaded blowout tees.
- Open a downstream zone valve BEFORE you open the air. This is the rule people skip. Start the zone at the controller (or open its solenoid manually) so the air has somewhere to go the instant it enters the pipe. Charging a closed system and then opening a valve slams a pressure spike into the fittings.
- Set the regulator, then open the air slowly. Dial in 50 psi for poly or up to 80 psi for PVC before connecting, then crack the ball valve open gradually rather than snapping it.
- Run each zone for no more than about two minutes at a time. Air moving through a dry plastic pipe generates heat and there is no water left to carry it away; a long dry run can soften a poly fitting or a nozzle. Watch the heads: they will spray, then mist, then blow dry air. Stop within a few seconds of the mist ending.
- Work from the zone farthest from the compressor back toward the nearest, then repeat the whole circuit a second time. One pass rarely gets everything, and the second pass takes seconds per zone.
- Close the blowout port, open the drain valves, and leave the zone valves in the position your controller manual specifies — usually with the solenoids relaxed and manual bleeds cracked.
The safety part, stated plainly
Compressed air is not a gentler version of water pressure. It stores energy, and a fitting that lets go under air becomes a projectile rather than a leak.
- Wear eye protection. CSU Extension flags this explicitly, and it is the one piece of gear most homeowners skip. Blowouts throw grit, and pop-up bodies eject at speed if a riser fails.
- Never stand over a sprinkler head while a zone is being blown out. A pop-up under air can fire its internal assembly upward hard enough to injure. Stand off to one side, and keep children and pets out of the yard for the duration.
- Never blow air backward through the backflow preventer. Beyond the equipment damage, you are pressurizing a device whose entire job is protecting the drinking water supply.
- Do not exceed the pipe rating to "get it done faster." Faster is more CFM, not more psi. OSHA's own compressed-air rule for cleaning, 29 CFR 1910.242(b), caps dead-end pressure at 30 psi with effective chip guarding and PPE — a useful reminder of how much energy is in even low-pressure air.
- Depressurize before disconnecting anything. Close the air, bleed the line at the port, then break the fitting.
If any of that reads as more risk than you want to own, that is a reasonable conclusion. A professional blowout in most US markets runs roughly $75 to $150 for a typical residential system as of July 2026, and the contractor arrives with a compressor that can actually clear a zone.
Do not forget the backflow preventer — it is the expensive part
The backflow assembly is the device that keeps irrigation water, and anything dissolved in it, out of your drinking water. It sits above ground in most installations, holds standing water in its body, and is made of brass or bronze that cracks rather than flexes. It is the single most common freeze casualty and the most expensive one.
Drain it according to its type: open the test cocks a quarter turn, set both isolation ball valves to roughly 45 degrees, and remove any bell housing so water cannot pool. In mild regions an insulated pouch or a wrap of pipe insulation inside a weatherproof cover is usually enough. In cold regions, many installers remove pressure vacuum breaker and reduced-pressure assemblies entirely and store them indoors over winter — check whether yours is designed for that, because reinstalling a testable assembly may require a re-test by a certified tester in your jurisdiction. Annual testing of backflow assemblies on potable connections is mandated by most US water utilities and by plumbing codes; confirm what your local water authority requires before you take one off the wall.
Hoses, drip lines, timers and spigots
Most freeze damage bills are not for buried pipe. They are for the cheap things nobody thought about.
- Disconnect every garden hose. A hose left attached keeps water sitting against the valve seat of the spigot, and a frost-free sillcock cannot drain with a hose on it. This is the number one cause of burst pipes behind exterior walls. Coil hoses and store them somewhere above freezing so the tubing does not go brittle — see how long a garden hose lasts.
- Bring timers, filters and pressure regulators indoors. These are plastic housings full of trapped water and they crack first. Pull the batteries while you are at it.
- Open the ends of drip mainlines so residual water drains rather than sitting in low spots, and blow drip zones at very low pressure only — 20 to 25 psi is plenty, and many installers simply drain drip rather than blowing it. Details in how to install drip irrigation.
- Drain and store rain barrels and any pump feeding them.
What to do differently at spring startup
Charge the system slowly. Open the main valve maybe a quarter turn and let the mainline fill over several minutes rather than in one surge — the water hammer from a fast fill breaks more fittings than the winter did. Run each zone and walk it, looking for a head that will not pop, a geyser where a body cracked, and dry patches that signal a broken lateral. Reset the controller schedule for spring rather than resuming July run times, and if you want the arithmetic done for you, the sprinkler run time calculator converts your soil type and precipitation rate into minutes per zone.
This is also the moment to fix what winter revealed. EPA WaterSense notes that a household with an automatic irrigation system that is not properly maintained and operated can waste up to 25,000 gallons of water annually — a single broken head or misaligned nozzle accounts for a startling share of that.
More from this hub: watering and irrigation · how to fix a broken sprinkler head · best sprinkler controllers · what a sprinkler system costs · how we rank.