How to Winterize Your Sprinkler System

close-up of a sprinkler head with water spraying out of it

Lawn sprinkler systems make summer lawn care so much easier, but shutting them off for the winter can be a mystery. If you live in colder regions of the country, it’s important to winterize your sprinklers this fall to avoid damaging your system. 

3 ways to winterize your sprinkler system

Sprinkler winterization methods depend on what type of system you own. Some systems have automatic drains, but others require a little more elbow grease. If you don’t have an automatic drain system, the other two methods will get your system winter-ready.

Here we will cover three different methods:

  1. Automatic draining method
  2. Manual draining method
  3. Compressed air method

1. Automatic draining method

  1. Turn off the water to your irrigation system. (Turn the handle 90 degrees, perpendicular to the pipe.)
  2. Turn on a sprinkler head.
  3. Let the system release excess water.
  4. Turn off your controller. 

2. Manual draining method

If you’re expecting a cold fall evening, protect your backflow preventer with this method. When you have time, you can blow out your pipes and turn off the system later in the season.

  1. Locate your water supply line. (This is usually located in the basement, a utility closet, or your crawl space.) Turn off the water supply to the irrigation system. (Turn the valve handle perpendicular to the pipe.)
  2. Go outside. Turn the backflow preventer valves to 45 degrees. 
  3. Turn test cock screws on the backflow lines to 45 degrees to let them drain. (If you don’t have a flathead screwdriver, use a small coin.)
  4. If you have a faucet next to the backflow, open it to drain any water still in the line. Also, open any drain screws at the ends of pipes to release that water.
  5. Find the valve box in the lawn. Open the manual drain in the manifold, and let it drain. Leave it open for the winter season.
  6. Go to the basement again (or utility closet, crawl space, etc.). If you have a faucet or drain screw, open it to drain the water. (Take a container to catch this water.)

3. Compressed air method

Safety first: This method can be dangerous. Some say homeowners should leave this job to the professionals. If you want to DIY, wear eye protection to ensure your safety.

Caveat: Every system is slightly different, but the basic winterizing principles are the same: You want to shut off the water to the irrigation system, expel water from the pipes and sprinkler heads, and drain water from the backflow preventer. Then, shut down the controller for the winter.

Equipment:

  • Pliers
  • Wrench
  • Flathead screwdriver
  • Bucket or pail
  • Air compressor
  • Compressor adapter

Pro Tip: If you’re unsure how your system works, hire an irrigation professional and take notes. Next year, you can do it yourself. 

  1. Shut off the water to the irrigation system. This valve will usually be in your basement or in the ground in a valve box near the water meter. Turn the handle to a 90-degree angle.
  2. Once you’ve turned off the water, open any drain screws on the lines in the basement or outside to drain trapped water. Leave a bowl under the drain screws in the basement to catch residual drips after you open drain screws or test cocks near the backflow preventer.
  3. Check your manufacturer’s instructions for the compression tolerance of your components. As a general recommendation, PVC pipes can withstand air pressure up to 80 PSI, but polyethylene pipe only takes up to 50 PSI. 
  4. Close the valve to the backflow preventer so your compressed air will not travel to your backflow device.
  5. Remove the cap to the blowout line.
  6. Twist on your compressor adapter. Connect the air hose.
  7. Turn on the zone farthest away from the compressor. (You don’t want to deliver compressed air to a closed system.)
  8. Turn on the compressor. Run a 2-3 minute cycle for the zone furthest from the compressor. Repeat for each zone, working your way back toward the compressor. If water remains after three minutes or so, go on to the next zone. After you’re done with all zones, run another cycle through each zone. Multiple 2-3 minute cycles are better than one 5-6 minute cycle.
  9. Turn off the compressor. Disconnect the compressor and adapter. Replace the cap loosely to leave room for water to drip out.
  10. Turn ball valves on either side of the backflow preventer to 45 degrees. Turn each of your test cocks to 45 degrees.
  11. Go back to the basement or to the valve box at the water supply. Grab a bucket, open the drain, and let any remaining water drain from the line.
  12. Turn off the system.

Do I need to winterize my sprinkler system?

If you don’t use your underground sprinkler system over the winter, then yes. Draining your pump is always a good idea. According to Clemson University, even ¼ inch of water can crack a pump casing in freezing weather.

Draining your pipes is usually done, but not always. If your frost line is only 6 inches deep and your sprinkler lines are buried at 12 inches, you may not need to drain your pipes. (The frost line is simply how deep the ground freezes in your area.) Most of the country has a frost line of greater than 12 inches, though. So for most people, draining pipes is recommended to prevent water from freezing and cracking the lines.

If you live in a subtropical paradise where it never freezes, you’re off the hook; this article is not for you. If your area drops to 32 degrees Fahrenheit or below, plan to winterize.

When should I turn off my system for the winter?

Once temps start to dip between 35 and 40 degrees, it’s time. Or, if your grass has gone dormant and you no longer need to irrigate. In either case, if you’re hiring out the work, get on the schedule early to avoid the winter avalanche.

Should I insulate my above-ground pipes?

Yes, you will want to insulate your backflow preventer pipes that live outside. Freeze damage can lead to costly repairs, especially if your backflow preventer is damaged. Buy foam pipe insulation wrap and secure it with foam insulation tape. The materials should cost less than $25.

If you need a little help with the last cut of the season, contact one of our local lawn care pros. They’ll get your lawn ready for whatever the winter may bring.

Main Photo Credit: Ted Erski | Pixabay

Sarah Bahr

Sarah is a writer who has previously worked in the lawn care industry. In her spare time, she likes to garden, raise chickens, and mow the grass with her battery-powered lawn mower.