Winterization of your residential irrigation system is a requirement for those living in climates that experience winter temperatures below 0 degrees Celsius. The following steps will ensure a clean start up in the spring.
First you will need to turn off all of your water sources that feed your system. Keep in mind that some systems will have multiple sources, all must be shut off before proceeding or you could have a nasty mid-January surprise involving an ice covered driveway and possible liability issues if someone slips and falls.
Make sure that your backflow prevention devices are shut to off. If you have externally located valves it is vital to leave the on/off handle(s) at a 45 degree angle to ensure that water does not get trapped between the casing and Teflon seal. If you do not do this you will likely find a replacement job awaiting you next season, as the brass casing will be cracked.
Purchase or rent an air compressor can push a large volume of air but at a lower operating pressure than is factory. An ideal compressor would be one that is a 185 cfm at anywhere from 75 to 90 psi. Before slowly opening the valve on the compressor, open an irrigation valve in order to prevent the mainline from becoming overcharged. Next you want to open up all of the low- volume drip valves to allow them to purge as the rotor and spray stations are engaged automatically. If they are rigged with flush valves, you want to flush the lines and let the emitters to expel the small amount of water that they house before closing the manual bleed screw to snug.
You are now ready to begin blowing out the heads. You can run the system in auto from the control panel safely with the water off and the compressed air on, or if you like you can run each head manually ensuring a clean blow. Be certain as you go that all water is blown free of the system. You can determine this by watching for the water to stop and a fine mist replacing it. Once blown clean, collect all of your tools and diagrams or instructions, along with your rain sensor (if equipped) and store in a location that will be ideal and functional come charge up time in the spring. A good place for these items might be your irrigation tool box or perhaps just inside the control panel door, there is nothing as frustrating as trying to remember where you put all of your gear come spring.