How to Winterize Your Lawn Sprinkler System

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A sprinkler system is a great way to ensure a beautiful yard, with its timed watering it will keep your lawn healthy and green all summer long.

Come autumn, however, you will have to prepare your system for winter lest it freezes and becomes irreparably damaged.

If the frost in your area extends below the depth of the irrigation piping, then winterizing the system is absolutely crucial. Water in the pipes will expand as it freezes, and as a result, will crack the pipes.

 Of course, you can hire an irrigation specialist or landscaper to do this, but if you want to save yourself some money, you will do it yourself.

The main action you will take is blowing the water out of the system. This will require an air compressor.

If you own one, you’re off to a great start. If you do not own an air compressor, you can easily rent one from a local home improvement store. You will also need an air hose.

There are different ways to go about this: manual drain method, automatic drain method, and blowout.

Each irrigation system is designed with the winterization process in mind, so when it was installed, the specialist would have told you which method to use. If you’re not sure, then the blowout method is the way to go.

Manual Method

The manual method is used when manual valves are at the end and low points of the piping. To drain these systems, shut off the irrigation water supply, and open the manual drain valves.

Once the water has been drained from the mainline, you’ll have to open either the boiler drain valve or drain cap on the stop and waste valve, depending on what is used in your area.

Then drain all remaining water between the shutoff valve and backflow device.

Should your sprinklers have check valves, you’ll need to pull up on the sprinklers so as to let the water drain from the bottom of the sprinkler body.

Ensure no water is left in the piping or backflow. Then close the manual drain valves.

Automatic Method

Use this method when the (automatic) drain valves are located at the end and low points in the piping.

When the pressure in the pipes is less than 10 PSI (pounds per square inch), the valves will automatically open and drain.

These will be activated by shutting off the irrigation water supply, and activating a system to relieve the pressure.

When the water is gone from the main line, open the drain valve on the boiler or stop and waste valve, (whichever you have), drain all remaining water between the shutoff valve and backflow device.

If your sprinklers have check valves, you’ll have to pull up on the sprinkler so water can drain out the bottom. Some regions may have a combination of manual and automatic drain.

Blowout Method


The blowout method uses an air compressor (with cubic foot per minute rating of 80-100), and compressed air may cause serious injury to the eyes from flying debris. For this reason you must wear safety gear including eye protection.

Do not stand over any irrigation parts during this process including pipes, sprinklers, and valves. It can be done at home as a DIY project, but it is recommended that you hire a professional to do this, due to the risk of injury. If you do not own a compressor you can rent one.

To begin the process, shut off the irrigation water supply and attach the compressor to the mainline. With the compressor valve in closed position, attach the compressor hose to the fitting.

Activate the sprinklers or zone highest in elevation and farthest from the compressor. Then close the backflow isolation valves, and slowly open the valve on the compressor.

This will gently introduce air to the irrigation system. The blowout pressure should never exceed 80 PSI, and must remain below the maximum operating pressure specification of the lowest pressure-rated component on each zone.

Each zone should also be activated by starting farthest away from the compressor and slowly working your way to the zone closest the compressor.

Each zone will be activated until there is no water exiting the heads, and once the station is dry, you should cease to blow air through the pipe.

Compressed air in the dry pipes will cause friction, and heat from friction can cause damage. This takes approximately two or more minutes per zone. Remember it is better to use a few short cycles per zone than one long cycle.

Once the water is removed, disconnect the compressor and release any air pressure. If your backflow device has ball valves, then open and close the isolation valves several times to release any trapped water.

Leave these valves open at a 45 degree angle (half open) and open the test cocks.

Keep an eye on the air compressor at all times. Do not stand over any component parts while the system is pressurized with air. Make sure all manual drain valves are closed after the blow out.

Finally, blow out the system, then drain the backflow or pump: do not blow the system out through the backflow or pump.

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