The frost line in the southern tier of states can be high enough that many homeowners do not think in terms of winterizing their sprinkler system. While we do not need to blow out or drain our sprinkler to protect from freezing we do need to protect the one major above ground component; the Plumbing Vacuum Breaker (or PVB). If you are in a norther tier with a frost line at or below 12 inches, click here.
This PVB should be winterized any time the temperature is forecast to drop below freezing. There are two techniques, depending on whether or not you have a main cut off valve.
A main shut off valve was generally not standard until it was required by the plumbing code in 2010. Generally, they are simple plastic gate valves (T handle) located under a round green cap on a line somewhere between the main water utility meter and the PVB valve. Some main water valves are located below the PVB.
These instructions assume that all sprinkler PVC pipes and zone valves are buried below 12 inches, except the pipe at the PVB, which is wrapped in foam pipe insulation.
If you have a main cut off, first turn it off. Than take a flat tip screw driver and turn both of the two small test valves (item 1) and let them run until the water stops. Then use the manual function of your control panel to run zone one for 5 seconds. This should relieve all of the pressure from your exposed sprinkler pipes and the PVB.
If you do not have a main cut off, first turn off valves 2 & 3 so that the handles cross the pipes. Then open the test valves (1) to bleed off water within the PVB. Next use the manual function of your control panel to run zone one for 5 seconds. Finally, return valve 3 to a position parallel with the pipe, but leave valve 2 across the pipe in the off position.