How to Winterize Irrigation Systems for Lawns? | Freeze-Proof Your Sprinklers

Winterizing irrigation systems for lawns means shutting off the water supply and removing all residual water from pipes, valves, and heads so freezing temperatures don’t cause costly damage.

For the full breakdown, see our best Air Compressor For Irrigation Winterization guide.

One night below freezing can crack buried PVC pipes, split sprinkler heads, and destroy a backflow preventer if water is left inside. The fix is straightforward, though it demands care: shut off the supply, drain or blow out every line, insulate what’s exposed, and kill the controller. Done right, the system survives winter untouched; done wrong, spring means digging up the yard. Here’s the full sequence that protects the investment.

Why Winterizing Matters Before The First Freeze

Water expands by roughly 9% when it freezes, and that expansion has nowhere to go inside a sealed irrigation line. The pressure can crack PVC pipe, split fittings, and shatter sprinkler heads and valves. The damage isn’t always visible at ground level, either, which is why a split mainline often surfaces only as a muddy patch in spring.

The controller left on is a common culprit in winter damage. An active controller can try to run a zone with frozen water in the line, which stresses the whole system. Turning it off also keeps the solenoid valves from holding water in a position where it can freeze. Texas A&M’s irrigation guidance for “light to mild freezing events” across much of the state leads with exactly that: turn off the controller, shut off the water supply near the meter or backflow assembly, and insulate exposed PVC and above-ground components.

The Three Methods: Drains, Auto-Drains, And Blowouts

Three approaches remove water from the lines, and each fits a different system design. The table below compares them at a glance.

Colorado State’s guidance is blunt: don’t trust manual or automatic drain valves alone. Those systems remove most water, but low spots and valve bodies still trap enough to freeze and crack. The university recommends blowing out the system with pressurized air as the dependable route.

How To Blow Out An Irrigation System: Step-By-Step

Compressed air is the gold standard because it clears water the other methods leave behind. The sequence below follows Hunter’s and Toro’s field guidance for a safe, complete blowout.

1. Shut off the water supply at the main shutoff or isolation valve, then turn off the irrigation controller so no zone activates during the process.
2. Attach the air compressor to the downstream blowout fitting, located between the backflow preventer and the first zone valve. Keep the backflow isolation valve closed or in its proper position so air doesn’t push water backward through it.
3. Introduce air slowly. Open the compressor valve gradually, then activate zones one at a time from the controller.
4. Start with the farthest and highest zone, then work toward the closest and lowest one. This pushes water downhill and out, rather than pooling it in lower lines.
5. Blow each zone until no water appears at the heads. Hunter’s guide says this can take about two minutes or more per station. Skip the pump, never blow from the backflow device, and keep manual valves closed once the zone is clear.
6. Disconnect the compressor and release trapped air pressure before moving on or storing the equipment.

Safety comes first, always. Wear eye protection and stand clear of sprinkler heads, since debris and water shoot out at speed. Pressure limits matter more than people expect: Texas A&M says not to exceed 80 psi for PVC or 50 psi for polyethylene pipe. Weathermatic’s spec is tighter, capping PVC at 75 psi and polyethylene at 50 psi, with airflow between 50 and 125 CFM. Hunter simply says never exceed 80 PSI and stay below the lowest-pressure-rated component on that zone. If the line reading climbs, throttle the compressor down immediately.

For manual drain systems, the routine is simpler but still methodical. Open all manual drain valves and drain the mainline, then open the boiler drain or stop-and-waste drain, and open the backflow test cocks. If the system has check valves, pull sprinklers up so water can drain from the body. Whether you drain or blow, once the system is dry, insulate above-ground backflow preventers and valves — Rain Bird specifically warns not to block air vents and drain outlets on the device. In freezing climates, shut off or drain bib taps and other exterior water sources, too.

If you don’t own a compressor large enough for the job, the practical route is to check the rental aisle or the tool you already have. A small pancake compressor often lacks the volume, not the pressure, to clear a full zone of heads.

Spring Startup: The Reverse Sequence

Come spring, don’t just flip the controller back on. Reopen the isolation valves slowly to let pressure build gently, then inspect every head and valve for leaks or signs of winter damage. Restore the controller and rain-sensor settings, and run a full cycle to confirm each zone operates. A slow startup catches a cracked fitting before it becomes a geyser.