One of the retired attractions at Disneyland was the “Carousel of Progress.” You’d sit in a theatre and watch an animatronic family as they described how technology was improving their lives, starting before the turn of the 20th century. Every rotation of the stage represented about 20 years of technological change, and the mechanical family’s clothing and home appliances would change accordingly, too.
It’s interesting to think about what an irrigation-industry “Carousel of Progress” might look like. Certainly, it would take us through the history of the development of rotating nozzles.
“Going back to the ’70s, Toro developed what they called their ‘stream rotor,’ recalls Chip Kah, president of K-Rain in Riviera Beach, Florida. “It was a multi stream sprinkler head. This multistream rotor was out before the single-stream rotor hit the market.
They were ‘adjusted’ with pattern plates—half-circles, quarter-circles, full circles.”
“Then the Walla Walla guys (Walla Walla Sprinkler Company, the inventors of the MP Rotator, which Hunter Industries bought the rights to in 2007) developed this viscous-damping technology, to keep the heads from spinning so fast. Then someone in their organization said, ‘Why don’t we take this viscous-damping technology and build a little multistream rotor?’” And the rest, as they say, is history. Every major irrigation component manufacturer now makes its own version of the multistream rotating nozzle.
Rotors and rotary nozzles The terms “rotor” and “rotary” are often bandied about interchangeably, but strictly speaking, they’re two different things.
A rotor is a sprinkler with a gear-driven body and changeable nozzles that emit water as a single stream over an arc that is more or less adjustable. A rotary nozzle, or rotator, puts out multiple streams of water as it rotates, and is installed on a stationary spray body.
Both types have low precipitation rates, meaning the amount of water emitted onto a designated area using head-to-head coverage is below one inch per hour.
“Rotors are used in applications where large areas of turf need to be irrigated, and greater coverage distance is needed, such as on athletic fields,” said Kelsey Jacquard, product manager for MP Rotators and sprays at Hunter Industries.
“Distances under 15 feet are best irrigated by rotary nozzles, and distances above 35 feet, by rotors. In between those distances, what type of sprinkler to use is a matter of preference by the designer or contractor,” Jacquard adds.
It would be impractical, for instance, to use rotary nozzles on playing fields. You’d simply have to use too many of them, and the physics just don’t work. You also want to minimize the number of things sticking up from the ground for ball players to trip over.
Rotary nozzles are typically used in smaller areas. There is a territory where single-stream rotors and multi-stream rotators cross over, and that’s when you look at watering radiuses of 15 to 35 feet. “For anything beyond 35 feet, you need a rotor,” said Orion Goe, product manager for The Toro Company’s Riverside, California-based irrigation division.
“At this time, there is no rotating nozzle, or any kind of nozzle, really, that can be retrofitted to a traditional spray body with a throw that exceeds 35 feet.”
In fact, Goe says, from 15 feet up to 35 feet, if you’re not going to use a rotor, a rotating nozzle is your only option, because there isn’t a spray nozzle that will go beyond the 17- foot range.
“The rotating nozzle fits that intermediate space, if you will, when an irrigator gets to the point where he says, ‘I can’t use a spray nozzle here, because I just can’t get the radius, but a rotor is more than I need.’” As for precipitation rates, rotors have interchangeable nozzles that allow you to adjust flow rates. You can get a precipitation rate as low as 0.3 inches per hour, or up to 0.8 inches per hour. Rotary nozzles are in the 0.4 to 0.8 range.
This is why some rotors and rotaries can be mixed together in the same zone, and still provide matched precipitation rates. But you can’t mix spray heads and rotors, or spray heads and rotaries, in one zone be cause the precipitation rates won’t match.
The most popular rotors are threequarter-inch inlet rotors. There are also half-inch (inlet) rotors. Goe says that ten years ago, these half-inch rotors were used to meet radius requirements of 15 to 30 feet. Over the last six or seven years, rotating nozzles have started to fill in that space.
Rotating nozzles are easier to maintain than rotors. If a nozzle ceases to rotate for some reason or gets clogged, it’s much easier to replace than an entire rotor.
“You can’t replace components on a rotor,” said Goe. “The whole thing has to come out, and a new one has to go in. From both a maintenance and a cost perspective, rotating nozzles make a lot of sense for 15-to 35- foot applications.”
Water conservation tools All of the major irrigation manufacturers say that drought concerns are driving up the sales of both kinds of rotating nozzles.
When asked what he thinks of rotating nozzles, Larry Hoekman, owner and president of LJH Landscape and Irrigation, Inc., in Beaverton, Oregon, doesn’t mince words: “I love them.”
So much, in fact, that he uses them almost exclusively on turf and ornamental beds and on all his new installations. They’re also his go-tos for retrofits and upgrades, whenever people are concerned about water conservation.
“And that’s something that’s on everybody’s minds now,” says Hoekman. “They’re saying that this coming summer may be very dry. If it is, we should expect watering restrictions.”
He takes that ball and runs with it, letting his customers know that rotating nozzles can reduce their water usage up to 30 percent. “It’s become a sales tactic for us.”
Kurt Hallisan irrigation consultant, designer and trainer, owner of Moody, Texas-based Water Management Specialists. His company is an authorized provider of training for contractors seeking their Texas irrigation technician licenses, one of the toughest state licenses to get.
“We have some very rigid laws in the state of Texas,” he acknowledges. That’s because Texas hasn’t just been hit by drought in the last
few years, it’s been clobbered by it. So, one of the things he teaches his students is drought management.
“The first thing you have to have is matched precipitation rates, period. That’s basic. Number one, it’s the right thing to do; and number two, in Texas, it’s mandated by law,” said Hall.
You heard right; matched precipitation rates are not just desired, they’re required. “What we’ve done in Texas, we’ve looked at the things that affect distribution uniformity. The elements driving that are: head-to-head spacing, matched precipitation rates, and controlled pressure.
When you put those three items together, you’re going to get the most efficient system you can get.” And, one that’s legal.
Hall says that with the drought, one of the biggest ‘uglies’ irrigators must face is the ‘watering window.’ If the watering window is only a few hours per week, they have to deliver the most water they can in that allotted time, with maximum efficiency. Rotators are very useful tools in meeting those watering windows, and still get the matched precipitation rates they’re required to have.
Greater efficiency Doug Donahue is an account manager at Ewing Irrigation Products, Inc., headquartered in Phoenix, Arizona. He also teaches certification classes through the Arizona Landscape Contractor’s Association. A 35-year irrigation-business veteran, he’s passionate about water management.
Throughout his career, he’s enjoyed wondering what the next exciting innovation will be. “What’s someone going to do with a spray head, a valve, or a controller that will be better than what we’ve always had up to this point? For instance, the MP Rotator, when it came out, was revolutionary for taking a sprinkler head and making it much more efficient than it had previously been.”
Donahue tries to convey to his students how big a step forward that was. “Traditional spray heads, as we know them and love them, are not very efficient. In fact, that’s an understatement. By replacing the spray heads with any of these high-efficiency rotating nozzles, you can almost double the efficiency of that spray system.”
The ultimate expression of irrigation inefficiency is runoff. It’s something he’s highly aware of, working in Arizona. Many areas there have ‘caliche,’ a type of soil that’s as hard as concrete. (We all know what happens when water hits concrete.) He likes rotating nozzles because their low precipitation rates match more closely soils’ ability to accept moisture and avoid runoff.
Chad Sorber is facilities manager at Oregon Health and Science University (OHSU) in Portland, Oregon. He can attest to the efficiency of rotating nozzles. Retrofitting the OHSU campus with them has cut the overall number of irrigation heads in half.
“We replaced a bunch of traditional spray heads that had 15-foot radii, and replaced them with rotary nozzles with 30-foot radii. We still have head-to-head coverage, with fewer heads to maintain and keep track of.” It’s also cut OHSU’s water usage substantially.
Retrofitting with rotators
Donahue sees huge profitability in the retrofit market.
“I’m in Phoenix. When I think about how many systems have been installed here over the last 15, 20, 25 years… it has to be in the thousands.”
This represents a great opportunity for contractors.
“All you have to do is take a look at all the commercial developments, HOAs and office parks in your area,” he says. “Wherever you see spray heads being used, tell those property managers that in some cases, just by switching nozzles, they can almost double the efficiency of their existing systems. You could carve out a nice little niche for yourself, just doing those retrofits.”
These are dollar signs that are flashing right in your face, says Donahue. If you’re maintaining an HOA or large apartment complex, or a group of them, that represents hundreds, even thousands, of spray heads you could be changing. If the owner or property manager is complaining about the water bill, that’s an open door to pitch a switch.
And, it’s easy to implement.
“Retrofitting rotary nozzles is very simple,” says Hoekman. “You just screw them right on. And in the case of the rotors, you just have to replace the body, and that’s a quick fix, usually with an adapter.”
Donahue tries to convey this to his students. “I tell them, in most cases, it’s as easy as just swapping the nozzles out. How hard is it to change a spray head nozzle? It’s not!”
Not ‘Blowin’ in the Wind’
Among Sorber’s responsibilities is the maintenance of the various “green roofs” around the OHSU campus and its affiliated hospital. One of the more recent green-roof installations faces the hospital’s fourth floor; patients can look out over this calming, verdant landscape.
It’s irrigated with multistream rotating nozzles. “They work really well,” said Sorber. “In fact, those types of nozzles are our preference for our green roofs in particular.”
Especially for one particular reason: “Up there on the rooftop, it’s a very windy environment. With traditional spray nozzles, a lot of the water will blow away without ever getting to the surface.”
Brent Barkley, product manager for rotors, spray bodies and standard spray nozzles at Azusa, California-based Rain Bird Corporation, explains why. “Traditional, standard spray nozzles are designed to operate at 30 pounds per square inch (psi); rotary nozzles, at 45 psi. The rotaries can handle a bit more pressure, and they can do it without misting and fogging.”
Smaller spray nozzles create a fan pattern, and if they’re over-pressured, they’ll start misting. A slight breeze will disperse those fine water particles. Rotary nozzles, on the other hand, are less pressure-sensitive to begin with. They create larger, heavier water droplets.
“With the larger droplet sizes, there’s less water that blows away,” says Sorber. “We’re using the water more efficiently, getting it to the root zones of the plants.” He likes the rotary nozzles so much, they’re fast becoming his preferred nozzles for OHSU’s regular landscape areas as well.
Some manufacturers make rotary nozzles that have long distances of throw: 25, 30, up to 35 feet. In this crossover territory, it’s your call whether rotors or rotaries would work best in a particular application.
“My personal feeling is that rotors are better suited for those kinds of distances,” said Barkley. “You’re taking water and throwing it pretty far. If you break that up into multiple streams, you’ll be throwing smaller water droplets out into smaller streams.”
“But if you collapse that water into one single stream, you’ll create more volume and generate larger droplets. There’s less chance for wind drift. You’ll also have to throw that stream at a lower trajectory, so it won’t get up into the air as high. It won’t be as susceptible to winds that might be ten or 15 feet off the ground.”
One contractor has still another reason for liking rotating nozzles. “Nine out of ten commercial properties that we deal with have systems that are 15 to 25 years old,” said Ed Malouff, head irrigation technician at Integrated Land Management in Tempe, Arizona.
Over the years, other large commercial developments have sprung up around those properties, drawing off the same city water main. After some time, the water pressure drops quite a bit below the level at which those old spray heads were designed to run.
Retrofitting with rotating nozzles gives the entire system a pressure boost, increasing the distance each head will throw. Not only that, the pressure is equalized among all the zones.
“As an example, if you had an area that was 10 feet by 15 feet, and you used a standard number-12 nozzle, it’ll give you a 12-foot throw, based on an average pressure of 40 to 60 psi,” says Malouff.
“If you were to put a rotating nozzle on that same zone, you could run it at 30 psi, and get one-and-a-half times the coverage that you’d have with a standard spray nozzle. It increases the pressure of the entire zone from 1.2 to 1.5 percent.”
Rotating nozzles, particularly the multistream rotaries, are getting more popular all the time. Barkley says that, quite apart from conservation concerns, people just plain like the way they look.
“Customers are demanding them, because they want to have the coolest looking sprinkler system on their block.”