In cold climates, underground sprinkler systems can freeze and burst in winter unless the lines are drained or blown free of water. An easy way to drain those irrigation lines is to install automatic drain valves. This is as easy as adding tee-fittings in the lower parts of the sprinkler system. If you live in an area where freezing sprinkler lines can be a problem, automatic drain valves could be the answer.
If you have an existing sprinkler system, it can be challenging (if not impossible) to determine where to install the automatic drain valves, as low points in the system can be difficult to find. Most homeowners are better off sticking with the more traditional method of blowing down the irrigation lines before winter arrives to remove any water. You can invest in a small compressor and do this yourself, if desired, for a more reliable method of keeping your sprinkler system from freezing. If you have a new sprinkler system, though, or if you have an accurate map of the system, installing automatic drain valves may work for you.
Two or three automatic drain valves per sprinkler valve are usually recommended in each zone if it branches off in different directions. Auto drains will work in almost all soil types, except maybe clay, and some even have back-flow preventers built in to stop any contamination from getting into the line. A cloth-like filter material usually covers the outside of the auto drain valve to prevent any dirt or debris from getting into the valve.
Because most pressurized water supply lines outside of the house, including those for irrigation lines, are installed below frost level, they are not prone to freezing. But the actual sprinkler lines are usually shallower and have to penetrate the surface, where the soil is typically colder. An automatic drain valve in these lines can help by draining the water down and out of the pipes before it can freeze. Here is a quick overview of how to install an automatic drain valve in a sprinkler system.
Source: The Spruce
