Step 1: When freezing weather is anticipated, simply turn off your main water supply to the irrigation system and make sure that the backflow device, valves, filter, pressure regulator, pipe, sprinklers, drip hose, and drippers are free of water.
Step 2: After the main water supply is shut down, run the timer/ controller through its normal watering cycle. This will allow each of the valves to open and relieve water pressure on the main line and valves. Allow the lines to drain slightly. After the timer/controller runs through its cycles, turn the controller off, or to Rain Off position.
Step 3: Through the height of winter leave the system off and drained. Water your plants with a hose only. In most cases, there is enough moisture in the ground from rain to sustain the plants during the extreme winter months.
The parts of the irrigation system that need to be drained:
Draining the main line: Some irrigation systems have manual drain valves or automatic spring-loaded drain valves at the end system that may not be installed properly and sometime will not guarantee that the main line will be thoroughly drained. Other probabilities are that the ground may not be flat or the drain valve may not be at the lowest point of the system. If the main line is installed below the ground, the only way to make sure that the system is drained of water is to use air pressure to flush the system.
Valve assemblies such as battery operated controllers or AC valves with a filter and pressure regulator: If the entire assembly can be easily removed from the pipe, it may be simple to store the assembly unit from the controller to the pressure regulator inside for the winter. If removing the filter assembly or valve assembly is not practical, the valve bonnet should be loosened or removed to make sure that the water from the top of the diaphragm and the filter cap are drained.
Drip tubing and micro tubing
First disconnect the drip tubing with the swivel adaptor from the filter assembly and make sure to wrap the swivel adapter or the connection to the filter assembly with a plastic bag to prevent dirt and contaminates from entering the drip tubing. If the drip tubing is installed above the ground, open all the ends of the drip tubing and allow the water to drain. Then lift the drip hose from the connection of the filter assembly, a few feet at a time and section-by-section, making sure that any water left in the drip tubing or micro tubing will drain out. After you finish draining the drip tubing and the micro tubing, make sure to close the ends of the drip tubing using the hose ends.