Sept. 26 2019 06:00 AM

There’s money to be made preparing irrigation systems for the season’s onslaught, but there’s much more to winterizing than simply hooking up a compressor.

Photo: Irrigation Tech

If you’re a “Game of Thrones” fan, you’ve heard the ominous expression “Winter is coming” uttered many times by different characters in the show — and it never means something good is on the way. But say those exact words to a group of irrigation contractors who work in the colder states, and they just might break out in grins. To them it means “time to make some fast money winterizing irrigation systems.”

It’s a ritual that must be carried out before the first big cold snap hits. The laws of physics are strictly enforced: Water expands when it freezes so it must be removed from irrigation systems before it can cause damage to pipes and components.

There’s lots of cold, hard cash in providing this service. It only takes about 20 to 30 minutes to do a residential blowout, and a technician can squeeze a bunch of those into an eight-hour day. At $80 a pop or more — well, you do the math. “A lot of contractors consider this their winter money,” says Chris Pine, CID, CIC, CLWM, CLIA, CIT, MCLP, CLVLT, owner of Blue Green Solutions in Pocasset, Massachusetts.

The blowout procedure

When contractors start winterizing for their clients depends on which region they work in; earlier frosts mean earlier winterizations. “We start doing high-priority systems the second or third week of September,” says Tim Black, president of Irrigation Tech, Rochester, New York.

He considers a high-priority system as one with a pump, some element of piping or a backflow device that’s exposed. All it would take is one night below freezing to have these things freeze and crack.

The winterization process for a residential system goes like this, according to Black. “First, we turn the water off in the basement or at the well or wherever the connection to the main is. Then we connect our compressor by a hose to the blowout point, which is installed just off the foundation of the house, near the backflow device.” (A quick-connect coupler can also be used for this.)

A compressor hose is hooked up to the blowout input at the start of the winterization process.
Photo: All-n-One Outdoor Solutions

Next, a technician turns on the compressor, activates zone one and watches until nothing but air is coming out of the heads. “We repeat with zones two, three and so forth until the last zone, and then turn off the controller, says Black. “An important point is that you need your compressor to be set for a high volume but a low pressure.”

The process isn’t that different for large commercial systems or athletic fields, except that there will be more zones and possibly more than one point of connection. “When we winterize a large soccer field, we take two compressors with us,” says Tom Horn, CIC, CLIA, CIT, founder of All-n-One Outdoor Solutions in Jefferson City, Missouri, and a Rain Bird Academy technical trainer. “That gets the whole thing done a little quicker.”

Chris Russo, northeastern field services manager at Hunter Industries, San Marcos, California, adds one more step. “Before you fire that compressor up, you need to stop at the controller and start up an irrigation program,” he says. “You don’t want to fire the compressor up with a closed system, because the air has no place to go. Then you’ve got problems.”

Black mentioned the two critical measurements: air pressure, measured in pounds per square inch, and air volume, measured in cubic feet per minute.

“The volume of air should be kept, depending on the size of the irrigation line, somewhere between 50 to maybe 80 cfm,” says Horn. “The air pressure should be a lot lower, somewhere down around 40 or 50 psi.”

Compressors should have pressure regulators. If they’re rentals, be careful to check the settings before using them, warns Horn, as they’ll often be set at an extremely high rate, 150 psi or more.

Sprinkler heads are designed to operate at 45 or 50 psi, and if you push 150 psi into them, you can damage them and the valves and possibly even rupture pipes. “Too high a pressure can turn sprinkler heads into rocket ships,” warns Black. “I’ve personally done it.”

“It’s very important to make sure the compressor has the ability to keep up with the volume of air that’s leaving the system,” adds Pine. “Large commercial systems may need a few hundred cfm or more.”

Before the techs at Atlanta-based Hydro-Tech Irrigation Co. set out for a day of winterizing at the company’s Virginia/Washington, D.C., branch, Vice President Philip Space has them make sure their compressors are set to 65 psi. “Eighty-five psi on a residential system is probably about the maximum,” Space says. “But we’ve seen damage done to seals or ratchet mechanisms on 12-inch spray heads when we get upwards of 85 or 90 psi.”

What if the system is full of MP rotators or other rotary-style nozzles? Russo says 65 psi is generally safe; Horn recommends 30 or 40 psi. Too much force can push the gear drives inside them apart. Pine says once the rotators start to spurt a little bit, it’s time to stop.

What about winterizing drip or low-volume systems and zones? Many contractors say that it’s really no different from winterizing conventional systems — but Pine and Horn disagree. “The air pressure should be much lower, around 20 or 30 psi,” says Horn, “or you risk damaging the dripline, the emitters or the low-volume microspray nozzles.”

Winterizing buried dripline is a challenge, because it’s not obvious when the water stops coming out. “You can’t see it and you can barely hear it,” says Pine. “But you should try to locate the end of the run so you can make sure all the water has drained out.”

Beware of hot air

Air coming out of a compressor causes friction, and friction causes heat. “Compressors produce very hot air, and that’s a problem, because we use plastic pipe that can melt,” says Pine. On a residential system, Horn recommends running a compressor no more than two minutes per zone.

It helps that blowouts are done when the air outside is usually colder. For a bit of extra insurance, many contractors will connect the compressor to the blowout tap with a length of hose long enough to give the air a chance to cool a bit before entering the system.

Horn has another caution: “If an irrigation system has a master valve, it’s usually close to the point of connection with the backflow preventer. If hot air is blown through that master valve for an extended length of time, it will usually damage its diaphragm.”

A large capacity compressor like this one is needed for doing system blowouts.
Photo: All-n-One Outdoor Solutions

Heat is no friend of rotary nozzles, either. “The components inside them are temperature-sensitive,” says Pine. “They’re not designed to have a large volume of hot air going through them.”

To further illustrate the danger of this, Russo shares this story. “During a winterization, the fellow who was running the compressor ran it at a much higher psi than we had in the past. The pipe became so hot that when it cooled down, it shrunk three sizes smaller in diameter — but the fitting it was glued to didn’t.” (The heat also melted the glue.)

He continues, “About an hour or so after they turned the system back on in the spring, a whole bunch of water poured out and washed out an entire hillside, because the pipe no longer fit inside the coupling.”

Not an option not to do it

Space has seen what happens when winterization isn’t done and a deep enough freeze occurs. “Hundreds of feet of pipe split open in a distinct spiral pattern,” he says. “The repair bill was in the thousands.”

Russo says in his part of the country temperatures can drop as low as the teens — yet still some people just won’t spend the money to winterize. But saving $80 or so just isn’t worth the risk. It’s a “pay me now or pay me more later” scenario.

A penny-pinching homeowner may be lucky enough to have a system comprised of polyethylene pipes, which Black says are a bit more forgiving than PVC, which “shatters like glass. Poly can handle a couple of freezes without breaking, but any more than that and they’ll give way.”

“A homeowner who tries to blow out his own system with a too-small compressor and doesn’t get it done right is a contractor’s dream,” according to Russo. All of those broken pipes, sprinkler heads and cracked manifolds are going to need to be replaced.
PJ Faust owns Terra Green Landscapes, in Charlotte, North Carolina. Because Charlotte is in the transition zone, “some contractors here promote winterizing, and others say you don’t have to do it at all,” says Faust. “We recommend it though, because every four or five years it’ll get cold enough to do damage, and you can’t predict when that’ll happen.”

It may cost a little bit — $100 for an average-size house — or more, if there are over 10 zones, but the components are going to last longer if they winterize.” Faust estimates.

Pine says that even in the transition zone, any exposed components such as backflow devices or pumps need to be winterized.

Warm and toasty backflow

Backflow devices, the things that keep contaminated water from washing back into the potable water supply, can be temperamental divas. They don’t like being the portal to the winterization process.

Many clueless homeowners attempting to winterize their own systems will hook a compressor up to a backflow device instead of a blowout tap. The outcome of that is often a very expensive lesson. “There are springs and diaphragms in the backflow, and they can get stretched,” says Russo.

Some techs will use a small “pancake” compressor at a very low pressure to blow water out of a backflow. But Pine says it’s never advisable to blow compressed air into these devices, as the risk of damaging the components inside is just too great.

Repairing a backflow unit will cost a couple hundred bucks wholesale, plus the markup and the charge for installation, says Faust. “If the entire unit must be replaced, then it could cost $500 to $700.”

Many contractors feel that the best insurance is to simply disconnect the backflow and store it inside the heated home or business for the winter. If a backflow device must remain outdoors, after the water is drained out, the ball valves should be left open at the 45-degree or halfway open position (0 degrees is fully closed; 90 degrees is fully open). That position will let any water that might get inside drain out.”

The colder the winter, the more protection will be needed. Russo advises against relying on the fiberglass covers many backflow devices come with, even when they’re lined with insulating material. The same goes for Styrofoam insulating sleeves. “Some people think that those things are adequate to protect a backflow from freezing, but they’re not,” Russo says.

Electrically heated enclosures, also known as “hot boxes,” are supposed to keep backflows nice and cozy all winter long. But Horn wouldn’t bet their survival on these things, either, saying that all it would take is a long enough power outage, and bye-bye, backflow.

As long as we still have winters, there will be a need for skilled irrigation professionals to perform thorough winterizations. For your clients, it’s cheap insurance against getting a nasty springtime surprise and the big bill to go along with it. We hope these tips help you have a profitable fall and your clients, a comfortable, freeze-free winter.

The author is senior editor of Irrigation & Green Industry and can be reached at

Flow sensors, pumps and LCD controller faceplates

There are some other things attached to irrigation systems that also require winterization. Flow sensors, for instance.

Norm Bartlett, founder of Creative Sensor Technology, Rochester, Massachusetts, and a member of the Irrigation & Green Industry Advisory Council, says some flow sensors work similarly to domestic water meters and have a large rotating impeller inside. That means “you have to be very careful not to over-spin that impeller and overheat the sensor during a blowout,” he says. The best way to do that is to check and see how close that meter is from the point where you’ll inject air into the system.

Photo: Irrigation Tech

“If the point in which the air is being injected is immediately upstream of the flow sensor, then it’s probably better to just remove the sensor for the winter,” Bartlett says.

Tom Horn, CIC, CLIA, CIT, founder of All-n-One Outdoor Solutions in Jefferson City, Missouri, and a Rain Bird Academy technical trainer, suggests removing the sensor’s internal components, capping it off until the blowout is done and then putting the internal components back in.

Centrifugal pumps need to be winterized as well. “You drain the water out of the impeller casing and remove the foot valve,” says Horn. “Then you turn off the power to the pump so it can’t be activated accidentally and run dry until it burns up.”

The final step is usually turning off the irrigation controller. But Horn says units with liquid crystal displays should be left on so the electrical current will keep them warm. “If the temperature drops to around 20 degrees or less, those crystals will freeze. Then, when you plug the controller back in the next spring, its display will be blank.” In areas with frequent or prolonged power outages, Horn recommends removing LCD face plates altogether and storing them indoors in a warm environment.