Irrigation Winterization


Get to that sprinkler system before it snows

In many parts of the country, cooler fall temperatures and cold rains have made irrigation a distant memory. While the heat of summer may be in the rearview mirror, the irrigation system that helped you through those hot, dry months can’t be neglected.

With winter coming quickly, it’s important to protect that irrigation system from the cold. In large part, the winterization process means getting the water out of the system. Sounds simple enough, but experts say that contractors (as well as homeowners) make common mistakes when winterizing irrigation systems that can cause just as much damage as neglecting these systems.

Damian Zawacki, technical training manager with John Deere Landscapes, says the biggest mistake they see when it comes to winterizing irrigation systems is the use of too much pressure when blowing out water. “People think that if 60 PSI is good, then 120 PSI must be twice as good,” he explains. “While pressure is important when blowing out a sprinkler system, it’s really the volume of air, measured in cubic feet per minute (CFM), that’s more important. So, the more CFM you can get in a compressor, the better.”

A pressure gauge can help determine how many PSI are being forced through the irrigation system. Even when using a low-pressure setting, it’s important to never close all heads to avoid building up too much pressure within the system.

Typically, compressors with higher CFMs will feature a bigger tank, and the relationship between pressure and CFM is sort of like a teeter-totter, Zawacki adds. “If you get more pressure from your compressor, typically your CFMs are going to go down. If you require less pressure from your compressor, typically your CFMs are going to go up.” He recommends using the regulator on the compressor to set an air pressure that’s roughly equivalent to the water pressure at that site.

“The most common error that contractors make when winterizing is using too much pressure and not enough volume,” agrees Sam Moore, national/northwest field service manager with Toro Irrigation. “Guys might have a compressor that doesn’t have enough volume to adequately blow out the system, so they’ll just keep increasing the pressure until things start happening.”

The use of high pressure, especially with too little volume, carries two risks. First, it may simply not work. Without enough CFM, water may remain in the irrigation system. Second, the irrigation system components can be cracked or destroyed, exactly the type of damage that winterization is supposed to help prevent.

“I used to think it was pretty cool to see the heads slam up and start misting, but that really wasn’t the correct way to do it, and in the spring I would see a lot of damage,” says Moore. “What you should do is start by pressuring the system with the minimum amount of air pressure that’s required to turn on the sprinkler heads. Find out how many heads your compressor can blow out with 40 to 60 PSI, and then keep working with that number of heads at all times. If you start at the highest valve, you’re going to move the water from the valve to the last head on that line. Then, before you turn the last head off, you start with the next zone. You don’t want to shut all the heads off and build up too much pressure.”

Some experts recommend keeping external controllers powered up in the winter to produce a small amount of heat that will keep moisture from damaging electronics. Others advise shutting the power off to avoid attracting rodents and other pests looking for a warm place to ride out the winter months.

The winterization process is also a great opportunity to take inventory of the system. “To winterize, you’re going to have to operate every head, whether it’s a fixed-spray or a rotary. You may find there are issues with broken or damaged sprinkler heads, so you can set that up for repair the next spring,” says Moore. “You can also look at coverage to be sure it’s set up correctly.”

Moore adds that after taking stock of the system and preparing to blow it out, it helps to drain as much water as possible from a low point in the system, the process of blowing the water out will be quicker and more effective. It can also likely be done with lower pressure, thereby reducing the risk for damage.

There can be serious damage from using too much pressure when blowing out irrigation system. “Once you start getting up to 70 or 80 PSI, you actually have a very hazardous situation,” says Moore. “You can actually start launching components up out of the ground.”

Because of these dangers, Hunter Industries urges contractors to protect themselves when blowing out irrigation systems. “Compressed air can cause serious injury, including serious eye injury, from flying debris,” advises the irrigation system manufacturer. “Always wear ANSI-approved safety eye protection, and do not stand over any irrigation components (pipes, sprinklers and valves) during air blowout.” Hunter adds that the compressor should never be left running and unattended during the winterization process.

While this time of year is critical for irrigation system protection, one important step in preventing damage during the winter must take place at the initial installation. “Many sprinkler heads have both bottom or side inlets. If all the sprinklers are installed using the bottom inlet, that lets air go through the bottom of the sprinkler and then up and out the nozzle, but if the head is installed using the side inlet, when you go to blow it out before winter, the air pressure will make a right turn and go up through the nozzle without getting out the water at the bottom of the sprinkler head,” John Deere’s Damian Zawacki explains.

He says the water that remains in the head can then freeze and crack the head, leading customers or contractors to complain that the system was properly blown out, but the heads still ended up broken. “When you dig the head up, you’ll usually see that it was installed using the side inlet,” says Zawacki. For that reason, he recommends that heads be installed, especially in northern climates, using the bottom inlet. “It may be a little tougher to install, because maybe you have to dig a little deeper, but that way when you winterize you’ll know that you’re getting all of the water out.”

If an installer insists on using the side inlet, they should include an automatic drain on the bottom of each head to drain any residual water,” Zawacki urges. Without that drain, if the system was installed using side inlets, there’s little more that can be done, other than blowing the system out to help remove water at the bottom of each head. “Some contractors will step on the heads to help flush the water out, but that’s not a good idea because you’re usually doing more damage than good,” he cautions.

Once a fine mist is visible from the head, it’s time to move on. Trying to get every drop of water out of the system by running the compressor after water has been removed on a given zone can actually heat up the pipes and damage components in the system.
Large irrigation systems, such as those at schools, parks and corporate offices, may require large compressors with sufficient volume to blow out the pipes and heads.

Zawacki recommends that contractors, before they leave the site, put a clear and prominent tag on the master shutoff valve stating something to the effect of: “Do not open.” This can prevent the homeowner or a member of the grounds staff at a commercial property from accidentally opening the valve and sending water back into the irrigation system during the winter.

Believe it or not, there is such as thing as doing too good a job when blowing water out of the irrigation system. “Don’t just sit there blowing out one zone for half an hour,” warns Zawacki. “After a while, if there’s no water in the pipes and you’re still blowing it out, that air has a tendency to heat up and that might damage or melt the many plastic components in an irrigation system.” The friction of the air movement can actually melt the irrigation pipe.

Moore adds that, though tempting, it’s not a good idea to try to get every last drop out by blowing the system out twice: “It’s important to be thorough the first time and resist the temptation to go back through the system again. Once you have a fine, foggy mist coming out of the head, you’re done. Open up another head, shut the other one off and keep moving down the line.”

Both Zawacki and Moore say that the electronic components in irrigation systems typically require little winterization work. “If the controllers are out in the field, we recommend leaving them powered on. It keeps them a little warm and keeps the condensation out, but I’ve seen cases where keeping them on attracts critters trying to get warm. So, some people prefer just to shut everything down, and I can’t fault them,” Moore explains.

A compressor with high volume (cubic feet per minute) and operating at a proper pressure (roughly the same as the water pressure at the site) can help blow water out of the irrigation system without damaging components in the process.

“The old-school guys usually keep the electronics on, because many electronic controllers had the transformer built in. The transformer produces a minute amount of heat, which dries any small amount of moisture in the controller, but today’s controllers are so well manufactured that you don’t really need to worry about that,” says Zawacki.

When following the proper steps and using the right amount of pressure, irrigation winterization is a relatively straightforward process. “It’s not rocket science. After you’ve done it a few times, it’s pretty easy,” says Zawacki. “Some systems claim that they’re self-draining, and people in some parts of the country don’t think they need to winterize their systems, but it’s really not worth the risk. It’s worth spending the little bit of time and money to avoid an expensive repair.”

Patrick White is a freelance writer and editor who has covered every aspect of the green industry in the past 13 years. He is based in Middlesex, Vt., and is always on the lookout for unusual stories.