HOW TO PROTECT YOUR IRRIGATION SYSTEM IF TEMPERATURES DROP BELOW FREEZING
Go through these steps to prevent any damage to any part of your system exposed to atmospheric temperatures (i.e. above ground pipes). Anything underground will be completely safe until temperatures drop below 20 degrees for a few nights in a row.
Throw a blanket over your vacuum breaker, pipes, or anything that is exposed to atmospheric temperatures.
Turn your water off that goes outside and open the petcock valves on your vacuum breaker (there are to) to release pressure.
Run your system through a cycle and pull the plug from underneath your vacuum breaker to drain it.