At the end of the “Rock and Roll Fantasy Camp” episode of The Simpsons, The Rolling Stones’ Keith Richards explains why he needs to get back home to England: “I’ve got to put the storm windows up,” he says. “Winter’s coming!”
The joke’s funny because you can’t picture the Stones’ lead guitarist doing anything more to prepare for winter than maybe, adding more scarves. Non-rock stars, however, who live where winter starts with a capital “W,” do have lists of winter chores: buy snow tires, get flu shots, examine mittens for holes, and yes, put up storm windows.
Irrigation contractors have winter checklists, too; they’re called “winter shutdowns.” This process, when done properly and early enough, protects their clients’ irrigation systems from seasonal damage. It’s kind of like giving them flu shots, increasing their immunity to freezing conditions.
The item-by-item shutdown list varies a bit from contractor to contractor, with some general similarities.
“The first thing I do is turn off the water mains to the house or building,” said Matthew Wendell, owner of The Sprinkler Guy, Anchorage, Alaska. “Then, I open the test cocks on the backflow preventers.”
Next, he finds the drain valve. “A typical house here has one in the crawlspace or basement. I open that up, and back-drain the water between the outside and inside of the house, so that there’s nothing left between the walls.”
Once Wendell has done that, he hooks his air hose to the port on his compressor. “Then, I walk around the yard. I use the controller to start the sequence, and turn on each zone for about a minute. On large systems, to speed up the process, I’ll open up multiple zones, so I can blow out three at a time.”
At the end, to signify that he’s all done, he sets the test cocks on the backflow preventer to the half open/half closed position (45 degrees), and turns off the controller. “For a residence, the whole process usually takes me anywhere from ten minutes to an hour, depending on the size of the system.”
“Every home is different,” said Brett McClellan, owner of Bozeman, Montana-based Gallatin Green Sprinklers, LLC. “It could be hooked up to a well, or a water line. Most homes here have the water main hooked right to a pressure vacuum breaker backflow (PVB) assembly, mounted about a foot above the ground.”
After he finds the hookup for the water main, usually in the crawlspace, he shuts it off. Then, he looks for the drain valve in between the main line and the PVB, opens it, and expels the water from the device. “That way, I know there’s no water pressure on the exterior of that PVB, going through the wall, because that can freeze as well,” said McClellan.
He then connects his compressor. “The hookups will vary depending on the home, but generally, the down pipes will have a three-quarter-inch plug, or a 3RC.” Or, none at all.
“Typically, there’ll be a blowout point right outside the house, so we don’t have to drag hoses indoors,” said Don Dahlk, coowner and operator of Capitol Lawn Sprinkler, Inc., Verona, Wisconsin. “If not, we’ll have to tap into the system, and install a blowout tee.”
“The other not-sogreat scenario is when we have to go in through the basement, hook a bunch of hoses together, and blow it out from there.
We’d rather take care of business outdoors, so we’re not messing up the customer’s house, going in and out with wet shoes and tracking grass clippings.”
After turning on all the zones, either manually or by using the controller, McClellan turns the compressor on and runs it for about 15 to 20 minutes. Working one zone at a time, he’ll blow each one of them out individually for about ten more minutes, until he knows for sure that all the water has been expelled. Then, he too sets the test cocks on the PVB to a 45-degree angle, and turns off the controller.
Bob Kerns is owner and president of Custom Turf, Inc., a Pittsburgh, Pennsylvania company that does irrigation, landscape lighting and lawn treatment. His company’s blowout routine is slightly different.
“First, we’re going to remove the backflow device, so that we don’t push any air through it,” he says. “Because of our hilly terrain, we use a lot of RPZ (reduced pressure zone) backflows, and they have all sorts of rubber seals and plungers. Pushing air of any velocity through those devices has a tendency to dislodge or tear those rubber pieces.”
Kerns’ blowouts are complicated by ‘deduct’ meters, common in the Pittsburgh area, that measure just how much water is expended for irrigation, so it’s not charged on the sewer bill. These meters must be A compressor is hooked irrigation system to disconnected before blowouts, as pressurized air would damage them.
Before he starts the compressor, he activates the first zone, so air pressure doesn’t back up against a closed system. “If the system’s not open, the pressurized air can damage the fittings or pipes.” He sets the compressor somewhere between 55 and 75 psi (pounds per square inch), depending on the size of the system. “Any more pressure than that causes friction that could damage fittings, heads or valves,” says Kerns. Next, he runs through each zone of the system from the controller, until each zone is flushed.
Some homeowners, in an attempt to save money, will try to blow out their own systems. These screw-itup-yourselfers often end up spending three or four times what they would have paid a professional to do properly in the first place, fixing what subsequently froze.
“Most homeowners don’t own big enough compressors,” said McClellan. “You need a high volume of air to blow systems out properly. Those home-store units, with the two little tanks, can’t pressurize the lines fully to evacuate all of the water.”
Wendell has seen this happen many times. “They’ll try to use the standard air compressor that you buy for power tools,” said Wendell. “Then they’ll be calling you next spring, to come repair the $350 PVB they broke. But they often don’t make don’t have repair parts, so you just have to replace the whole thing.
It’s an expensive fix.” If you’re going to do blowouts, you need something that really blows. It’s not the psi, or pounds per square inch, that’s so important; rather, it’s the total volume of air, the cubic feet per minute (CFM), that a compressor puts out Be prepared for when that makes the difference. Without sufficient volume, air will blow right over the water in the pipes without pushing it out.
“It happens every year, without fail,” says Kerns, wearily. “I’ll have one or more customers telling me that he owns a compressor, and he can get that thing up to 125 psi. That’s nice, but there’s no volume; it’s probably putting out five CFM, which just isn’t going to cut it.”
Then what does he find come spring? “Damaged heads, mainlines, laterals and valves. Those repairs can easily be a couple of thousand dollars.” Not really worth it, just to save $75 to $100!
What’s needed is the kind of tow-behind, industrial-grade compressor that can displace the high volume needed, up to 185 CFM. McClellan has one (as do many other contractors), it was expensive, costing him $20,000. You might be able to find a used one for much less, or you can rent one.
It is possible though, to have too much of a good thing. Once a zone is dry, you should turn the compressor off. Why? Basic physics. Compressed air blowing through dry pipes creates friction, friction creates heat, and heat causes damage.
And it’s not just pipes that can be impacted. “As a manufacturer, our biggest concern is too high a pressure, for too long; that can cause internal damage to sprinkler heads,” said Troy Leezy, marketing manager at Hunter Industries, San Marcos, California.
“A professional contractor that’s experienced in winterization knows exactly when to stop. However, we’ve seen examples where people have run compressors until they’ve melted the plastic internals in the sprinklers’ gearboxes, fused them together.”
Leezy explained that the gearbox, in the lower part of the sprinkler itself, has a little turbine in it. As water flows through the sprinkler, it spins a little shaft in the reduction gearbox; that gives the turbine its torque.
The water also lubricates the sprinkler head. Under too high a volume of air, the turbine will spin much quicker than it normally would, causing friction buildup and a potential meltdown. It’s more of an issue for traditional rotor sprinklers and rotator heads than sprays.
A big blowout
McClellan says the winter shutdown process for a large commercial site isn’t that different from that of a residence.
“Some of my big real estate developments have anywhere between 20 to 50 valves. When there are that many, I’ll turn on the controller, and run through all the zones electronically. Otherwise, I’d be walking around a huge, five- or ten-mile complex, manually turning on all those valves.”
“Usually, these are on super-deep wells,” says McClellan. “There won’t be a PVB, but there might be a dualcheck backflow device. There’ll be an on-and-off switch, a ball valve, that’s generally down at the base of the well. Sometimes there’s a valve box, too.”
“But it’s the same concept. I shut off the main water supply, hook up my compressor to the 3RC, and blow out all the zones.”
Again, we need to stress having enough air volume. It’s even more critical with larger sites. “We own a smaller 85-CFM compressor,” said Dahlk. “But then we’ll rent several 185s so that we can do both our residential and our larger commercial sites.” Dahlk’s company services around 2,500 commercial accounts.
“Some of the larger commercial sites have a half or three-quarters of a mile of two-inch-wide mainlines running through them. You want something that’s got enough push behind it. Sometimes we’ll even use two 185s on those.”
Kerns says that some commercial systems have remotes that allow a technician to “see” each individual zone. This saves him from having to walk back to the controller each time he runs a zone.