Without proper preparation your sprinkler system can be damaged by freezing temperatures. Here are some tips from Rain Bird on how to prepare your irrigation system if you live in a region where it freezes.

1. Insulate your assets.

Shut off the water supply to the irrigation system. The main shut off valve for your irrigation system needs to be protected against freezing. To prevent it from freezing make sure it is wrapped with insulation (foam insulation tape and a plastic bag), or somehow protected from freezing. If you do not have a main shut off valve, consider it a preventative investment. Any above ground piping needs to be insulated. Self-sticking foam-insulating tape or foam insulating tubes commonly found at home supply stores, are fine.

2. Stay in control.

If you have an automatic system then you will need to "shut down" the controller (timer). Most controllers have a “rain-mode" which simply shuts off the signals to the valves. The controller continues to keep time, the programming information (start times, valve run times, etc,) isn't lost, and the clock continues to run. The only change is that the valves will not activate. If your controller is responsible for activating a pump, as a precaution, remove the wires that are connected to the MV and common. This will prevent the possibility of the pump from being activated which could cause overheat damage.

An alternative to using the rain mode is simply to shut off the power to the controller. If you do, you'll need to reprogram the time and potentially all your other settings as well, in the spring.

3. Drain the pipes.

Now you need to remove the water from the pipes and sprinklers so that it won't freeze and break the pipe. There are several ways to drain your pipes: the manual drain valve, the automatic drain valve or the compressed air blow-out methods. However, since there could be potential safety risks we recommend contacting your local irrigation specialist.

4. Protect valves and backflow preventers.

Insulate backflow preventers and valves if they are above ground. You can also use insulation tape for this. Do not block the air vents and drain outlets on backflow preventers.

"Blow Out" Method
It is recommended that a qualified licensed contractor perform this type of "Winterization" method, The blow out method utilizes an air compressor with a Cubic Foot per Minute (CFM) rating of 80-100 for any mainline of 2" or less. These types of compressors can be rented at your local equipment rental yard. The compressor is attached to the mainline via a quick coupler, hose bib or other type connection, which is located after the backflow device. Compressed air should not be blown through any backflow device. To start the "blow out", shut off the irrigation water supply and, with the compressor valve

in the closed position, attach the air compressor hose to the fitting. Activate the station on the controller that is the zone or sprinklers highest in elevation and the furthest from the compressor. Close the backflow isolation valves. Then slowly open the valve on the compressor; this should gradually introduce air into the irrigation system. The air pressure should be constant at 50 PSI. If the sprinkler heads do not pop up and seal, increase the air pressure until the heads do pop up and seal. The air pressure should NEVER exceed 80 PSI.

Each station/zone should be activated starting from the furthest station/zone from the compressor slowly working your way to the closest station/zone to the compressor. Each station/zone should be activated until no water can be seen exiting the heads, this should take approximately two minutes or more per station/zone. It is better to use two or three short cycles per station/zone than to have one long cycle. Once the station/zone is dry, you should not continue to blow air through the pipe. Compressed air moving through dry pipes can cause friction, which will create heat and the heat could cause damage.

Additional Steps
Once the water has been removed from the irrigation system, disconnect the air compressor and release any air pressure that may be present. If your backflow device, the most common backflow installed is called a Pressure Vacuum Breaker, has ball valves, open and close the isolation valves on the backflow device numerous times to ensure that any trapped water has escaped from the upper areas. Leave the isolation valves open at a 45° angle (approximately 1/2 open) and open the test cocks.