When should you shut down your sprinkler system and what is “winterizing”? Sprinklers should be shut down and winterized before the temperature drops below freezing on a regular basis. In Northern Colorado, this is usually in mid October.
Winterizing is a process in which the sprinkler line is turned off and the remaining water in the pipes is blown out of the line using pressurized air. After this is done, the backflow valves should be left 1/4 open and the backflow itself should be wrapped and insulated.