Before winter hits, it is important to removing any and all water from your underground sprinkler lines, otherwise that water will freeze when temperatures drop. And when water freezes it expands--meaning the pipes are at risk of rupturing, thus causing expensive damage to your system. Here is a DIY guide to winterizing your sprinkler using the blow out method.
The blow out method
The easiest way to remove water from your sprinkler system is known as the blow out method. This involves using an air compressor to literally blow excess water out of the pipes. This is accomplished by connecting an air compressor to the sprinkler line's blow out port. But before you get started, it's important to understand a bit more about what type of compressor you'll need.
Select the right sized compressor
Not just any air compressor is capable of generating the pressure necessary to completely clear out your sprinkler's network of pipes. The power of an compressor is expressed in terms of its cubic foot per minute rating, or CFM. You will need an air compressor with a CFM between 80 and 100, assuming your mainline has a diameter of less than 2".
Also be aware that the pressure introduced by your compressor should never exceed the maximum operating pressure of your sprinkler system. Consult your owner's manual if you are unsure of this value. In no case should pressure exceed 80 PSI. Otherwise you risk damaging the components of your system.
Attach the compressor to your system
All automatic sprinkler systems have a so-called blow out port located on the main sprinkler line coming out of your house. In order to connect your air compressor to the blow out port, you will first need the appropriate adaptor. Because all air compressors have a standardized interchange, the adaptor you need will be determined by the type of blow out port on your system.
Once your compressor is connected to the system, be sure to close any backflow valves. This will prevent the air from pushing backwards into the water supply pipes. While this wouldn't necessarily hurt anything, it will reduce the effectiveness of your blow out.
Proceed carefully zone by zone
Depending on the size of your lawn, your sprinkler system consists of multiple zones. These can be controlled using your system timer. When blowing out your system, be sure to open just one zone at a time. Otherwise the air pressure will be too diffused to properly remove any standing water.
Once the lines are connected and you've selected your first zone, turn on your compressor. You should see the sprinkler heads in that zone pop up and discharge a spray of water. As soon as the water has stopped blowing out, switch off the compressor. Left on too long, the pressurized air will generate heat that can melt the internal components. For assistance, talk to a professional like Outdoor Service Inc.