If freezing temperatures are forecasted, and your irrigation system has not yet been winterized, you will need to drain the backflow prevention device to prevent freeze damage to your system. 

IMPORTANT: Draining your backflow is not a substitute for a complete blowout and winterization. 

Step 1) Locate the main irrigation water shutoff. If inside the house, it is often located near the water meter and/or main water supply line, or in the basement ceiling.