How do I winterize my system?
There are several things that must be done to winterize a sprinkler system. The first step is to determine if the system uses auto-drain valves. If auto-drain valves are present, then all you need to do is turn the main water supply off, and then loosen the solenoid on each valve to let air inside. The water should flow down hill and out of each zone through the auto drain valve. You may have a manual drain for the main line between the shut-off valve and the valve manifolds. If a valve is present, open it to allow all water to drain. If you system does not use auto-drain valves, then an air compressor must be used to blow the water out of the zones. Turn off the main water supply to the sprinkler system, and hook up an air compressor to the system. Pressurize the tank to about 50 psi and then open one of the valves manually. Run that station for 2 to 3 minutes to allow all the water to be removed from the system. Shut that valve off and wait for the compressor to pressurize again. Repeat for the next zone. After all zones are empty, loosen the solenoids to allow air to enter the top of the valve. This is a general guideline for winterizing a system. You system may require additional steps depending on the particular installation.  Note: This process requires large capacity air compressors with an air flow rate between 4 and 8 cubic feet per minute.  Small, consumer air compressors will not be able to perform this task correctly and can often damage the sprinkler system.  Never exceed the recommended PSI or you may risk melting or exploding your sprinkler pipes and heads. Because of the complicated nature of this process, we recommend contacting an irrigation professional to have these services performed.  Always wear saftey glasses and gloves when performing sprinkler repairs. 
Winterizing Video
 
 
Click here to view Orbit's Winterizing Guide.