How to Blow Out Your Irrigation System Before the First Frost

I-Irrigation lines that hold water through the winter are a ticking time bomb for your plumbing. When water freezes inside your pipes or sprinkler heads, it expands with enough force to crack PVC, shatter valves, and blow out seals. Dealing with those leaks in the spring is a chore no one wants, and it usually involves digging up your lawn to find the break. Winterizing isn't about getting the lines bone-dry; it is about removing enough water so the remaining droplets have room to expand without exerting pressure on the pipe walls. Done correctly, a blowout gives you peace of mind that when the thaw comes, your system will fire up on the first try without any surprise geysers.

  1. Lock Down the Water First. Locate your main irrigation shut-off valve, usually found in the basement or a utility box near the street, and turn it to the closed position. Open one drain valve at the lowest point of the system to allow the majority of the water to gravity-drain.
  2. Seal the Compressor Tight. Attach your air compressor hose to the blowout port (usually a quick-connect or threaded adapter located near your backflow preventer). Use a coupling that matches your specific port type to ensure an airtight seal.
  3. Find Your Perfect Pressure. Adjust your compressor's regulator to 40-50 PSI for PVC pipe or 25-30 PSI for flexible poly pipe. Never exceed 50 PSI, as higher pressure can damage internal components like solenoid valves or plastic sprinkler nozzles.
  4. Push the Water Out Systematically. Manually open the first zone on your irrigation controller and slowly introduce air into the line. Keep the air flowing until the sprinkler heads in that zone are only spitting mist, then switch to the next zone.
  5. Leave Nothing Behind. Wait for each zone to run for about 2-3 minutes or until no more water is expelled. Repeat this process until you have cycled through every single zone in your entire system.
  6. Seal the System Safely. Disconnect the compressor and open the blowout valve to bleed off any residual pressure. Turn your irrigation controller to the 'OFF' or 'Rain/Winter' mode to prevent it from cycling during a warm spell.