Every year, before the first freeze, the ritual of irrigation "blow out" becomes the priority for all irrigation systems that are in regions of the country where the frost level extends below the depth of the installed piping.
Even if you have drained some water out of the system, the remaining water can freeze, expand and crack the PVC piping (rigid, white pipe), usually from fitting to fitting. Polyethylene pipe (flexible, black pipe) is used in many freezing climates. Although polyethylene pipe is more flexible and can expand under pressure, water left inside could freeze and rupture the pipe walls. Freezing water in the backflow assembly will damage the internal components and could possibly crack the brass body. To minimize the risk of freeze damage to your irrigation system (heads, valves, lateral lines), you’ll need to "winterize" your irrigation system. It would be best to use the blowout method to ensure all the residual water is out of the system. Learn more