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You can sense it in the air. That nip you feel when you take a deep breathe as the sun goes down a little bit earlier every day. Yes, autumn has come to an end and you are at the doorsteps of the long cold winter months ahead. With this realization comes the need to winterize your irrigation system so it can endure the bitter weather and be ready to work properly once spring rolls around again.
Whether you live in a temperate climate or you will be digging yourselves out of the white stuff for 5 months, the steps to winterize are vital to the health of your irrigation system. Depending on what part of the country your irrigation system is located, different approaches are necessary.
When manual valves are located at the end and low points of the irrigation piping, simply shut off the irrigation water supply and open all the manual drain valves. Once the water has drained out of the mainline, open the boiler drain valve or the drain cap and drain all the remaining water that is between the irrigation water shut off valve and the backflow device. Then, open the test cocks on the backflow device.
When you have pulled up on the sprinklers to allow the water to drain out the bottom of the sprinkler body, close all the manual drain valves.
Automatic drain valves will, by design, open and drain water if the pressure in the piping is less than 10 PSI. Shut off the irrigation water supply and activate a station to relieve the system pressure. Once the water has drained out of the mainline, open the boiler drain valve or the drain cap and empty the remaining water that is between the irrigation water shut off valve and the backflow device. Then, open the test cocks on the backflow device. In some areas you might have a combination of the manual drain system on the mainline and auto drain system on the lateral lines.
When blowing out the system with compressed air, always wear ANSI approved safety eye protection and do not stand over any irrigation components.
The blow out method utilizes an air compressor attached to the mainline via a quick coupler, hose bib or other type connection. Shut off the irrigation water supply and, with the compressor valve in the closed position, attach the air compressor hose to the fitting.
Close the backflow isolation valves, and then slowly open the valve on the compressor. Never exceeding 80 PSI, the blow out pressure should start out low and gradually increase.
Start from the furthest station from the compressor, and work your way back. Take approximately two minutes or more per station, and stop when no water can be seen exiting the heads, since compressed air moving through dry pipes can cause friction, heat, and damage. Once the water has been removed from the irrigation system, disconnect the air compressor and release any air pressure that may be present.
In temperate climates, it is not necessary to remove the water from the underground pipes since they will not freeze.
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Colder climates will have to perform this yearly, keeping careful attention to water removal and pipe integrity. Your backflow preventer, along with any above ground pipe, should have permanent insulation installed to protect from those unexpected early and late season freezes. There is the option to install pipe-heating cables on the above ground valves and backflow preventer, as well as insulation over the heater cables. However, the constant use of electricity is expensive, and you run the risk of pipe breakage if there is a power outage. Winterization, if done properly can end up saving you money and headaches over the course of a year. If you follow the procedures above, no matter if you are in Georgia or in Michigan, you will be able to prevent damage to your irrigation system. So zip up your jacket before you get a cold, and get a move on. Winter waits for no one.
Francisco Uviña, University of New Mexico
Hardscape Oasis in Litchfield Park
Ash Nochian, Ph.D. Landscape Architect
November 12th, 2025
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