How to Winterize a Sprinkler System

Prepare for cold weather and prevent damage to pipes with our guide to winterizing a sprinkler system.

lawn sprinklers flowers grass maintenance

Dave Toht

Sprinkler systems are an excellent way to ensure your lawn and garden remain green and lush throughout the hot summer season. The water lines run underground to evenly spaced sprinkler heads, making it easy to water the yard. Bigger yards might even have a sprinkler system with distinct zones, so only one zone is watered at a time. Additionally, some sprinkler systems pair with an automatic timer for a set-it-and-forget-it operation.

However, when cold temperatures hit, a sprinkler system needs to be turned off, drained, and insulated to prevent ice from forming inside the pipes. If a sprinkler system is not properly winterized, any remaining water will freeze and can damage the pipes and components of the system. To ensure your irrigation system is properly prepared for winter, follow this guide to winterizing a sprinkler system.

Methods for Draining a Sprinkler System

There are three main methods for draining the water out of a sprinkler system, including automatic draining, manual draining, and blowout draining.

Automatic Draining

This can only be done with sprinkler systems that have an automatic drain function. This feature makes it easy to drain the sprinkler system by turning off the water supply and running the sprinkler heads to reduce the water pressure. Automatic draining then begins to clear the pipe of excess water.

Manual Draining

This is an option if your irrigation system is equipped with a manual drain valve. Simply turn off the water supply and open the manual valves at the ends and low points of the piping. Also, make sure to drain the backflow device.

Blowout Draining

This method typically takes the least time, though it's the most complicated method for draining a sprinkler system. This method uses an air compressor to blow air into the sprinkler system in order to force the water out through the sprinkler heads.

Turn off the water supply and connect the air compressor to the sprinkler system after the backflow preventer. Turn on the sprinkler head that is elevated the highest and furthest away from the air compressor, then slowly open the compressor valve to add air to the system. Make sure the air pressure does not exceed the pressure specification of the irrigation system. Continue to add air to the system until water starts coming through the sprinkler head. Blow out each sprinkler head one at a time for about two minutes each or until water is no longer coming out, then close the sprinkler head and move to the next. Once you have gone through all sprinkler heads, turn off the compressor and close all valves on the irrigation system. 

sprinkler installed in lush grass by tree
Laurie Black

When to Prepare a Sprinkler System for Winter

It’s important to take steps to winterize the system before freezing temperatures hit, otherwise, it may be too late to prevent damage to the sprinkler system. However, if you winterize the irrigation system too soon, your lawn and garden may suffer at the tail end of the summer. Wait until temperatures consistently dip down to between 60 to 65 degrees Fahrenheit to winterize a sprinkler system.

Keep in mind that you will need to have some tools and supplies on hand in order to drain the water from the sprinkler system and insulate any above-ground components that would otherwise be vulnerable in freezing weather. If you aren’t blowing out the water lines, the system can take up to 24 hours to fully drain, so a good rule is to winterize your irrigation system as soon as fall ends. Don’t wait too long to prepare the sprinkler system for winter if you want to avoid damage to the pipes, fixtures, and other components.  

How to Winterize a Sprinkler System

To ensure it doesn’t develop leaks, cracks, or other damage due to ice buildup, it’s necessary to winterize a sprinkler system. Follow these steps to learn how.

What You Need

  • Channel locks
  • Wrench
  • Air compressor
  • Insulation tape

Step 1: Inspect System

Inspect the irrigation system before beginning the winterizing process. This will give you the opportunity to check for any leaks or existing damage that might need to be repaired. Keep in mind that if the water lines are leaking, water may be able to enter the system even after the water supply is closed and the pipes are drained. If this occurs, the water can freeze and cause additional damage, so repairing any cracks or leaks before winterizing is recommended.

Step 2: Shut Down Water

If the sprinkler system doesn’t need any repairs, the next step is to turn off the water to the sprinkler. Check inside the home for an isolation valve on the water line leading to the sprinkler system. Turn off the valve to stop the flow of water into the irrigation system.

Step 3: Turn Off Timer

Not all sprinkler systems have an automatic timer, but if your system does have a timer, it will need to be turned off or set to rain mode. Rain mode essentially allows you to power down the timer without losing any programmed information or settings.

Step 4: Drain Water 

Draining the water from the irrigation system is the bulk of the work to complete the winterization process. Check to see if you have an automatic or a manual drain that can be used to quickly and effectively drain the system without the use of an air compressor. 

If you have an automatic drain, simply run the sprinkler heads to reduce the water pressure and allow the automatic draining process to clear the excess water from the pipes. If your system relies on a manual drain, open the manual valves at the ends and low points of the piping to drain the water from the pipes. It’s also important to make sure you drain the backflow device.

For sprinkler systems that do not have an automatic or manual drain, use an air compressor to blow water out of the lines. Connect the air compressor to the sprinkler system after the backflow device, using the hose bib or a quick-connect coupling. Open the irrigation station that is elevated the highest and located the furthest from the air compressor, then close the backflow isolation valves. 

Turn on the air compressor and slowly start to add air to the system, progressively adding more until the water starts to spray out of the open sprinkler head. When the water stops spraying out, open the next sprinkler head and close the previous one. Repeat this process with each sprinkler head until the entire system has been blown out. Make sure to keep the air pressure below the maximum operating pressure of the lowest-rated part of the system to avoid damaging the components. 

Turn off the compressor and disconnect it from the system, then release any pressure left inside the pipes by opening and closing the valves on the backflow device. Finally, close all of the valves on the irrigation system to prevent water from entering the lines. 

Step 5: Wrap Insulation Around Above-Ground Components

The last step in the process is to wrap any above-ground components that would otherwise be exposed to freezing winter weather, such as valves, water lines, and the backflow preventer. Wrap these components with foam pipe covers or insulation tape. Just make sure that you don’t block any air vents or drain outlets during this process. 

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