Step 1: Shut Off the Water
It will come as no surprise that the first step is turning off the water to the system with a main valve that’s usually found near your water meter. If your system has valves to prevent backflow, shut these off, too. There are usually two of these valves that lead into the backflow device; be sure to shut them both off. If your system doesn’t use potable water, it might not have a backflow preventer.
Step 2: Turn Off the Timer
If your system runs on an automatic timer, make sure you shut that off, too. Some systems have a “rain mode” that allows you to essentially power down the timer without losing any programmed information or settings. Allowing the system to run in rain mode throughout the winter is usually safe and shouldn’t run up your energy costs. In the spring, you can turn the rain mode off, and the timer should resume working normally.
Step 3: Drain the Water
It’s not enough just to keep water from flowing into the system; you also need to drain out the water that’s already in there. This is the biggest and most time-consuming step in the process, but it’s absolutely vital. There are three main methods of drainage depending on what type of sprinkler system you have.
Some sprinkler systems may allow you to drain the water manually. These systems have shut-off valves at low points or ends of the piping. Make sure to wear eye protection while completing this step because the water supply in the system is under pressure. Slowly open the valves one at a time and let the water run out, then close them when finished.
Other systems have components that will automatically drain the water once the main valve is shut off and the water pressure drops. You can usually activate the system by running one of the sprinkler heads with the water supply off.
However, there will still be some water trapped within the valves themselves. Locate the solenoid on each valve—a plastic cap with wires coming out of the top—and loosen it. This will allow air to flow into the system and water to flow out.
Some sprinkler systems allow you to hook an air compressor up to the pipes to force the remaining water out of the sprinkler heads. However, this method is destructive and even dangerous when tried on a sprinkler system that isn’t built for it. Additionally, it’s worth mentioning that a typical DIYer’s air compressor might create the 50 PSI (pounds per square inch) of pressure needed to clear out PVC piping. However, at-home machines can’t usually generate the 10 CFM (cubic feet per minute) of volume needed to quickly and completely blow out the water.
For these reasons, we don’t recommend attempting the blow-out draining method on your own. Even if you don’t damage the system, you might not get the job done completely, and even a little water left in a sprinkler system over the winter can cause problems. Hiring a professional for this job is a once-a-year cost that’s well worth it.
Step 4: Insulate Above-Ground Components
Finally, make sure that all the above-ground parts of the sprinkler system are properly insulated from the weather. The main shut-off valve, plus any exposed pipes or backflow preventers, should be wrapped in foam covers or insulation tape. On the backflow preventers, make sure not to block any air vents or drain outlets.