To winterize a sprinkler system, turn the system's water supply and controller off, and remove the backglow prevent and anti-siphon valves. Use an air compressor to blow the water out of each valve in the system beginning at the backflow preventer.Continue Reading
Turn the water off at the main supply valve, and turn the sprinkler's controller or timer off by disconnecting the power source or setting the system to rain mode.
Remove the backflow preventer, drain it and store it in a protected environment, such as the garage. Remove the anti-siphon valve, and store it with the backflow preventer.
Use an air compressor that has a pressure of at least 50 cubic feet per minute and that features a working regulator and pressure gauge. Connect the air compressor to the backflow preventer riser, and open the valves beginning at the valve with the highest point in the system. Turn the air compressor on, and gradually increase the air pressure while remaining under 50 psi. If the air from the compressor becomes hot, connect a hose between the compressor and the sprinkler system. Continue until each valve in the system has been blown out. Close each valve, or cover the valve with a threaded cap.