Winterizing your sprinkler system must be done before the first freeze every year. Winterizing a system eliminates the potential for water to freeze in the sprinkler lines and valves. Water left in the lines and valves could freeze and cause them to split, which may go unnoticed until you turn on the sprinklers in the spring, only to see gurgling water fountains in the middle of the lawn.
The best way to winterize the sprinklers depends on how your system was designed. Here are some tips and guidelines that should work with most systems.
The goal for winterizing any irrigation system is to remove the water. No water means there will be no ice in the pipes. First, turn off the electrical controller. Some valves can be damaged if they run without water, plus there is no need to waste energy on a box you aren’t using. Simply turn the switch to “OFF” or unplug the control box.
Turn off the water at the stop and waste, a valve that will be in most professional systems. Simply put, this is a valve that shuts off the main water to the sprinkler lines. It may also divert the remaining water in the line into a drain or other area. This should be at the lowest point of the entire system, to allow all water to seep out of the pipes.
Some municipalities require a backflow preventer; others do not. If you have one, open it. This device ensures that dirty water does not enter the city water supply by making sure the water only flows one direction. Typically, these will have small air inlet valves that allow air to enter the sprinkler lines, which allows the water to drain to its lowest point.
To give you an idea of what should be happening here, imagine taking the straw in your drink and covering the top end with your finger, preventing any air from entering the top of the straw. When you lift your straw out of the cup, the liquid remains in the straw. When you remove your finger and allow air to enter the top of the straw, the liquid will begin to flow out the bottom.
Open the sprinkler valves; they are typically located in a rectangle box somewhere in the yard. After removing the lid (carefully, because there are always spiders or other critters hanging out in the box) turn the knobs on top of the valves 1/4 – 1/2 turn. This allows more air to enter the system, allowing more of the water to drain out. Sometimes there is also a small “bleeder” screw on the control valve. This should also be opened to allow more air to enter the system.
If your system was installed correctly, this should be all you need to do. There should be several automatic drains in all the pipes that will open and allow water to seep out of the pipes, and into the soil. If you have any other valves, hose bibs, manual drains, etc, they should all be opened to aid in this draining.
Professional landscapers may also attach a large air compressor to the system. They use a significant amount of air and blow it through the lines. This will force almost all the water out of the sprinkler heads. Although this is the most thorough way to winterize a system, it is typically unnecessary if the system was installed correctly.