Hopefully your sprinkler system has served you well during the growing season. Now is the time to winterize so you will get many more years of good service. A little TLC before the freezing months will help prevent damage to seals and cracked pipes. While taking the time to winterize may seem daunting to you please know that fixing a broken underground system can be quite costly. That should provide enough incentive to protect your sprinkler system this winter.

While many systems may rely on gravity to drain water from pipes, the tubing can sink over the years causing water to pool. This remaining moisture can freeze and expand resulting in impairment to the system. To ensure that all water is out of the pipes it’s vital to flush with compressed air.

How to Protect Your Sprinkler System:

First Shut Off the Water

You underground sprinkler will have a shut off valve. Be sure you have turned the valve fully to the off position. If the system makes use of a pump, this mechanism will need to be drained and brought inside for the cold months. If it cannot be removed, you should wrap it in insulated material.

A Device for Backflow

Typically a sprinkler system will have an AVB (Atmospheric Vacuum Breaker) or a PVB (Pressure Vacuum Breaker which may be referred to as a reduced pressure device). If no backflow mechanism was installed, you can move ahead to the steps for removing water from the system.

Please note that PVBs shouldn’t be purged with compressed air. The raised temperatures from this process can cause them to melt. After the system has been cleared out, you can come back to the PVB turn the ball valves and test cocks several times. Leave them in a partially open setting to eliminate moisture build up.

Removing Water from the System

The use of compressed air is an efficient way to guarantee that water has been removed from the pipes and valves. It is important to note that both pressure and air volume needs to reach a certain point to thoroughly purge the system. The range of 40-80 PSI (pounds per square inch) is the goal. Most systems are designated with gallons per minute (GPM) rating per zone which should be indicated on the design plan or can be calculated via details on the manufacturer’s website.

You should use a compressor that delivers the proper CPM of air within the correct psi range. This is important because a smaller compressor is less efficient and can overwork the compressor. If the compressor is oversized, it will still work if fitted with a regulator.

Your backflow device will need to have a downstream blowout fitting. Attach the line from the compressor to the blowout valve. Check to ensure that the isolation ball cock is closed because any loose fittings could blow off unexpectedly. Now you can begin by turning on one or more of the zones at the controller and set the compressor to the proper psi. Start it up.

Typically you will need 2 short cycles of air to thoroughly clean out each zone. Once the zone has been blown out, do not do it again. This can result in a heat build-up.


Now you can disconnect the compressor. Double check to ensure that all valves on the backflow prevention device have been set to half open for the winter months. As an extra precaution, leave the controller plugged in because it produces a minute amount of heat that will help stop condensation from forming inside the device.

Set the controller to run at least one minimum cycle a week to keep the solenoid plungers from becoming jammed in one position. When spring rolls around, you will need to remember to return all the test cocks and ball valves to the closed position. This will need to be done before you pressurizing the system. When the water supply builds up, slowly open the ball valves to eliminate the possibility of water hammer impairment.


That’s it. You’re done. While all the psi and GMA lingo may seem overwhelming at first, after one stab at protecting your sprinkler system for the winter you have will the process down pat and manage it like a pro next winter. Be proud of your good work!