Winterizing an irrigation system

By Mike Lorenc, Conservation Garden Park


Not to bring anyone down, but winter is coming. Along with the recent stretch of rain and cold weather it’s time to start thinking about shutting down those irrigation systems that have kept our landscapes going through the hot months. Freezing temps can freeze the water in our irrigation lines, valves, or backflow prevention devices and expand until them until they break open. These can be a costly and time-consuming surprise next spring when you discover leaking pipes, broken valves, or worse, a broken backflow preventer.

You can avoid damage from water freezing your pipes by draining or blowing most of the water out of your irrigation system. Here are the steps:

1: Turn the system off. This may require finding the stop and waste valve—generally buried several feet deep—and using a long key to turn it off. This type of valve is designed to drain the main line when turned off. Other houses have a valve in the basement just before the main water pipe heads back out through the foundation and into the yard. Turn these off so that they are at a 90-degree angle to the pipe. Near this valve should be a drain valve, which usually looks like a hose bibb (faucet). Open that valve and drain the water into a container. Leave this open during the draining process.

2: Drain the water out. Open all your sprinkler valves. This will help drain the lateral lines into the main line and relieve the pressure. Leave those valves open all winter. If you have automatic drains installed in the low points of your system, your job is mostly done now. Those automatic drains help remove water from any low spots in the lateral lines. If you don’t have those installed, consider it for the future.

Another way to drain the water out of your system is by blowing it out with an air compressor. Blowing the system out is the surest way to make sure the water gets removed. It is also the most difficult and potentially dangerous if not done correctly. This requires an air compressor with enough volume to fill the pipes and push the water out. Most small compressors aren’t up to this task. Small shop compressors have pressure that is too high, and not enough air volume, so renting a bigger one or hiring a professional is the best option for blowing it out.

3: Protect the backflow prevention device. Not all houses are equipped with one of these but if you have one if does take some special care. These devices are heavy and break easily if not protected, and they are expensive to replace. That price tag also makes them attractive to thieves, so locking them down or removing them for the winter is a must. These are usually attached in such a way that they can be removed very easily, then they can simply be stored in the garage until spring.

If you have questions about winterizing your sprinkler system, you may have received an instruction manual when your system was installed. Review that for details or call your local sprinkler supply store.