How to winterize a sprinkler system and blow out lines
Winterizing your sprinkler system protects pipes, valves and lawn investments from freeze damage and costly repairs. This guide walks you through a safe, step-by-step blowout method and a few alternative options so you can choose what fits your equipment and comfort level. Allow about 1–3 hours depending on system size and gather a compressor, basic tools and protective gear before starting.
Step 1: Turn off the water supply
Locate the main irrigation water shutoff and close it completely to stop incoming flow. If you have an automatic controller, also shut off the controller or set it to “off” so no zones run while you work; this prevents accidental water entry during blowout. Doing this first minimizes pressure and water in the lines for safer handling.
[Illustration: hand turning irrigation main shutoff valve near meter or house foundation]
Step 2: Relieve system pressure
Open a manual drain or an aboveground bleed-off at the highest station to let trapped pressure escape; run any low-point drain valves until water slows to a drip. Wear goggles and gloves while releasing pressure; reducing pressure avoids sudden sprays when connecting equipment and prevents water hammer that can damage fittings.
[Illustration: gloved hands opening a brass bleed-off valve with water trickling out]
Step 3: Access the controller and valves
Open the irrigation controller box and disconnect the electrical supply or set controller to off to avoid accidental cycles. Walk the yard and open valve box lids to expose zone valves so you can monitor operation and check for leaks during the blowout. Identifying valve locations saves time and prevents missed zones.
[Illustration: open irrigation controller and a yard valve box with several solenoids visible]
Step 4: Choose and set compressor connection
Attach a rated air compressor with 30–50 psi regulator to the sprinkler system using a quick-coupler or adapter at the blowout port or anti-siphon drain; set initial pressure to 30 psi for pop-up heads and up to 50 psi for large-diameter PVC mains. Limiting pressure prevents damage to nozzles and seals; never exceed 80 psi and keep compressor duty cycles to recommended run/rest intervals (10 minutes on, 10 minutes off) to avoid overheating.
[Illustration: compressor with pressure regulator hooked to irrigation blowout connection]
Step 5: Blow out each zone sequentially
Start with the zone farthest from the compressor and run the compressor only while that zone is active; cycle each zone for 1–3 minutes until only air comes out of the heads. Move closer to the compressor as you progress. Staggered sequencing ensures water is pushed out toward the nearest exit and avoids pushing water backward into other zones.
[Illustration: sprinkler heads spraying air and mist with compressor hose connected nearby]
Step 6: Verify dry lines and cap openings
After each zone is cleared, inspect heads and lateral lines for strong air flow and no water droplets, then close the zone and cap or close the valve box lids. For systems with manual drain valves, ensure they are closed if directed by manufacturer or left open slightly to drain; dry lines prevent freeze expansion and cracked pipes.
[Illustration: hands inspecting pop-up sprinkler head with no water coming out, valve box lid nearby]
Step 7: Winterize controller and backup measures
Remove batteries from the controller and store them indoors; program a winter or off schedule to avoid accidental automatic starts. Drain or insulate any exposed backflow preventer and insulate aboveground piping with foam sleeves or heat tape per manufacturer instructions to guard against sub-freezing nights.
[Illustration: controller with removed batteries next to foam pipe insulation and wrapped backflow device]
- Mark valve boxes and the shutoff with flags for quick access in spring.
- Use a compressor with a 1-inch or larger coupler and a 50–100 ft hose for large systems to keep unit away from frost.
- Label each zone and note blowout pressure used so spring startup is easier.
- If unsure about compressor hookup, hire a certified irrigation pro for the blowout; cost is often $60–150 depending on system size.
- Wear ear protection near running compressors and goggles during pressure release.
- Perform blowout after several frost-free days so ground and pipe joints are dry and less likely to trap water.
- Never use household or small pancake compressors without proper regulator and fittings — excess pressure can rupture pipes and heads.
- Do not point compressed air directly at people, animals or fragile plants; flying debris or high-pressure blasts can cause injury.
- Never exceed manufacturer-recommended pressure (typically 50–80 psi) for your sprinkler heads and pipes; excessive pressure is the most common cause of winter damage.
- If your system has a pressure vacuum breaker or permanently installed backflow device, follow manufacturer steps — do not attempt to open or disassemble these parts without guidance as they can be damaged or cause contamination issues.
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