How to Winterize Your Irrigation System

Water, when trapped inside irrigation lines during a freeze, transforms into an expansive force capable of shattering PVC pipes, valves, and sprinkler heads. Winterization isn't just a maintenance chore; it is the single most important act of prevention you can perform to ensure your landscape survives until spring without costly underground repairs. Done well, this process clears the entire network of moisture, leaving only air behind. Focus on clearing the lowest points of the system and ensuring the backflow preventer—the most vulnerable piece of brass in your setup—is properly isolated and drained. When you finish, your pipes will be ready for the dormant months ahead.

  1. Lock out the water first. Locate the main irrigation shut-off valve, typically found in the basement, crawlspace, or a buried box near the property line. Turn the handle clockwise until it is fully closed to stop the flow of water into the system.
  2. Silence the timer now. Set your irrigation timer to the 'Rain/Off' position or disconnect the power supply. This prevents the system from attempting to run cycles while the main valve is closed, which can damage the solenoid valves.
  3. Release the backflow valve. Open the test cocks on the backflow preventer using a flathead screwdriver. Turn the isolation valves on the device to a 45-degree angle to release trapped water inside the ball valves.
  4. Hook up the compressor safely. Attach your air compressor hose to the blow-out port located after the backflow preventer. Ensure your compressor is set to a pressure no higher than 50 PSI to avoid damaging the internal components of your sprinkler heads.
  5. Push the water out completely. Start with the zone furthest from the compressor. Open that zone on your controller or manually turn the solenoid, then run the air until only a fine mist exits the heads, followed by dry air.
  6. Inspect every zone end-to-end. Cycle through each remaining zone in order, moving toward the compressor. Once all zones are clear, shut off the air and leave the test cocks on the backflow device slightly open to allow any lingering condensation to evaporate.