Photo courtesy: Rain Bird
The late comedian Rodney Dangerfield had a catchphrase: “I don’t get no respect— no respect at all.” For a long time, the same thing could be said of water. Certainly, we knew it was essential to life; however, we thought it would always be around, in abundance. Rather than show it outright disrespect, we simply took it for granted.
Not anymore. The days of overwatering and overflowing into the street are gone. Today, we have smart controllers, rotating stream nozzles, low precipitation rate sprinklers, soil moisture sensors and more. As an industry, we strive to show water the respect it deserves— and save our customers money—by using it more efficiently.
For irrigation contractors, installing water-conserving sprinkler heads is now becoming the norm, and low-precipitation-rate sprinklers are a big part of that. Before we start talking about these important devices, let’s define our terms.
Precipitation or application rate (these terms are often interchange able) is simply the rate at which sprinklers deliver water to a target area. A “matched” precipitation rate is when every head in a system delivers water at the same rate to the turf or plant material being watered. Distribution uniformity (DU), on the other hand, is a measure of how evenly that water is applied to the target area. A 0.7 DU is a realistic benchmark for an irrigation system comprised of spray head bodies with rotating stream nozzles.
When we say a precipitation rate is “low,” what does that mean? There is no universal definition, according to Brent Barkley, product manager for rotors, sprays and spray nozzles for Rain Bird, in Azusa, California.
He would generally classify anything under one inch per hour as “low precipitation.” Some municipalities that give rebates for installing low-precipitation-rate sprinklers have created thresholds at 0.75 inches per hour. Chip Kah, president of K-Rain, in Riviera Beach, Florida, says that “anything under one-half inch per hour, 0.5 and below, we would consider a low precipitation rate.”
When you talk low precipitation rates, you’re going to be talking mainly about rotary nozzles. It can get confusing, especially to the customer, when we throw out similar-sounding terms like “rotor” and “rotary” in the same sentence.
A “rotor” is a type of sprinkler that throws out a single stream of water, in a continuous left-to-right and back again motion, over and over as it moves along an arc. They’re used mainly when you need to throw water a long distance and cover a lot of ground, from 20 feet all the way to 100 feet or more; that’s why they’re a familiar sight in parks, sports fields and golf courses. Rotors give you the most coverage with the least amount of heads.
A “rotary” nozzle also rotates, however, these are generally used in smaller to intermediate-sized areas. Instead of throwing out one single stream, a rotary nozzle delivers multiple, individually distinct fingers of water as it revolves around a central axis. Most models have adjustable radii and arcs; some are even hand-adjustable,
requiring no tools. The rotating nozzle, designed to be installed on spray head bodies, was specifically designed to deliver a lower precipitation rate and higher DU.
A “spray” nozzle, however, does just that; it “sprays” water in a continuous fan pattern that can be radius-adjusted and in some cases, arc-adjusted.
“There are spray nozzles that some manufacturers say are ‘low precipitation’ as a feature highlight, but there are no true “low-precipitation-rate spray nozzles,” said Kelsey Jacquard, product manager for MP Rotators and Sprays at Hunter Industries, San Marcos, California.
The first rotating nozzle was manufactured by the Washington state-based Walla Walla Sprinkler Company back in the early 2000s. It was called the MP Rotator (MP, for Matched Precipitation). Hunter Industries bought the product in 2007, and has continued to add refinements to the original design. All the major irrigation companies now make rotating nozzles.
“The creation of the multi-stream rotating nozzle opened things up for
the under-20-feet-in-throw distance market that had been previously dominated by spray heads,” said Phil Sheppard, a Texas-certified landscape irrigation contractor and an Irrigation Association (IA) authorized instructor. He teaches irrigation at several colleges and at Irrigation System Solutions, the Coppell, Texas-based contractor training school that he owns.
“Lack of an intermediate solution gave irrigators little choice,” said Sheppard. “For example, say you had an area with lots of trees in the way. A contractor would have had to install sprays, because with the high-pressure streams that rotors generated, the streams would have stripped the bark off the trees.”
Sheppard says that about ten years ago, it was pretty much a given that for coverage of an area 20 feet or more across, you would always use rotors. “Those were the only sprinklers that would work correctly for you, back then.”
“For one thing, you’d need fewer of them; that means less piping, less trenching, less labor and less materials in general,” he said. “You would always use the largest head suitable for your application, and that was usually a rotor.”
“Now, however, we can use rotary nozzles on a lot of those areas,” says Sheppard. “Now they make ones that can water up to 35 feet away. It’s opened up a broad, intermediate-range market, and really changed the way that irrigation contractors look at doing irrigation now.”
Better uniformity According to Kah, there are a couple of things driving manufacturers to produce low-precipitation-rate sprinklers. “First, all of us are always looking for ways to improve DU. The second is a desire, starting in the West, to reduce overall precipitation rates.” Rotary nozzles, in particular, produce better uniformity along with lower precipitation rates.
“With spray nozzles, a very low precipitation rate is achievable,” said Jacquard. But there are lots of good reasons for choosing rotating nozzles over sprays.
“Rotators can reach as low as 0.36 inches per hour. They have a low precipitation rate, to allow for the soil to absorb the water as fast as the water is put out, eliminating runoff. Rotators also have a more uniform distribution of water than typical spray nozzles.”
In areas with very tight, clay soils, water needs to be applied very slowly, at an application rate that doesn’t exceed the soils’ infiltration rate, or runoff will result. Let’s define that term, too; “infiltration rate” is the ground’s ability to absorb the water that’s being applied to it. If you exceed that rate, you’re likely wasting water.
Uniformity saves water, period. If people see that an area of their yard isn’t as green as the rest, they will want to “correct” the problem. It’s psychological. But the way they’ll go about it is incorrect.
“Let’s say I put in a new sprinkler system at your house,” says Sheppard. “After awhile, you notice that your grass is getting a little bit yellow in one area, so you bump the controller up 15 minutes. Now you’re overwatering everything else, and getting overflow and runoff. We call that ‘watering to the drier area.’” This is why uniformity is key. The better uniformity you have, the less people will be tempted to “correct.”
Ron Payne, owner of St. John Sprinkler Service, LLC, in El Paso, Texas, uses rotary nozzles “when I run into a system that’s been over-designed,” where someone has installed more sprinklers on a zone than there is water available to flow through them. The only real way to fix that, according to Payne, is to retrofit those spray bodies with something that doesn’t use as much water—“and that’s usually rotating nozzles.”
“I tend to use rotary nozzles when I’m retrofitting a system that’s been built incorrectly,” says Russ Jundt, founder and president of Conserva Irrigation, Inc., Minneapolis, Minnesota.
Rotary nozzles are ideal for retrofitting. Perhaps because they came along later in the game, nearly all of them can be installed right on the same risers as the old sprinklers. They’re usually cross-compatible; you simply unscrew the old spray head and screw the new nozzle on, regardless of what brand of sprinkler was there before.
Here’s an example of a perfect retrofitting opportunity. A property owner notices that when his sprinklers are running, water is overflowing into the street. Or, someone else has noticed it, for instance, the local “water police,” and now, he’s getting fined for it. Whatever the reason, he wants that runoff to stop.
“The customer’s property may be on a slope, for instance,” says Jundt. “The flow rate from a conventional spray nozzle is so high that even if you tried to have very short run times, you’d still get erosion and runoff. In that case, I’d come in and take all the conventional nozzles out and put in rotary nozzles.” This drastically reduces the application rate, down to one-half an inch per hour as opposed to two inches an hour.
Even with a high application rate using rotors, a lawn’s thirst may not really be quenched. Sheppard says that a lot of people get “faked out” by a very fast rate of water hitting the ground, and everything getting wet on top. However, turf or plant material may not be getting wet at the root zone, and that’s where it really counts. Rotary heads allow more water to be absorbed.
Another place where low precipitation heads are ideal is when you don’t have much water to throw out there in the first place. “I’ve run into situations, like on some condo properties, where they only have three gallons per minute of flow available in which to water the lawn,” said Payne. “Rotating stream nozzles are ideal for that situation.”
Sometimes there’s low water pressure in a municipal system, say from overexpansion in a real estate development. That’s another good rotarynozzle retrofitting opportunity, according to Kah. “Instead of running 15 gallons a minute, now you’re running seven gallons. Since the application rate is much slower, you do have to run the system a bit longer to keep the plant material alive—but not twice as long, because the uniformity is better with rotary nozzles.” Mix and match?
Since what we want to achieve are matched precipitation rates, can we mix different types of sprinklers on the same zones? The answer is “Yes, but cautiously.”
“With careful design, and the right products, it is possible to match the precipitation rates of rotors and rotary nozzles, allowing them to be zoned together while irrigating different sections of an irregularly shaped lawn,” said Barkley. For instance,
rotors being used on a fairly large area of turf in a front lawn, with some rotary nozzles irrigating a narrow strip of side yard.
What you don’t want is a crazyquilt of different types of sprinklers with no particular rhyme or reason. A hodgepodge such as this is usually the result of many repairs and alterations done over the years by various contractors.
Judith Benson, owner and president of Clear Water PSI, in Winter Springs, Florida, sees a lot of crazyquilt layouts, especially on some older systems. “A lot of times, you’ll see where someone put rotors in to cover some of the larger areas,” says Benson. “So then they’re running sprays and rotors together, but the rotors are delivering water at a much different application rate than the sprays. There’s no uniformity.”
To correct the situation, she’ll remove the spray nozzles and replace them with rotating nozzles. This will help the system move closer to becoming a matched precipitation rate system. “We find that to be a fairly cost-effective solution,” she says, especially when compared to the price of putting in a brand-new irrigation system.
Benson also turns to rotary nozzles when she sees that spray zones are overextended, meaning that the spacing isn’t “textbook.” This can result in dry patches in the spots where you don’t have head-to-head coverage.
Growing segment Drought may not be nurturing to plants, but it’s helping the market for water-conserving sprinkler heads grow. Many municipalities have begun rebate programs, as they’ve seen that retrofitting with low-precipitation-rate sprinklers is a great way to conserve water.
“Toro has definitely seen its sales grow in this sector, because everyone is trying to use their water more efficiently, particularly the owners and managers of large commercial sites,” said Orion Goe, product marketing manager, residential and commercial irrigation, at Toro’s Riverside, California-based irrigation division. Strict watering guidelines, tiered rates geared to financially penalize water waste are part of the story. People don’t want to move into that second, third or fourth tier, where their water rates triple or quadruple.
Jundt says that many of his customers instinctively want lower-precipitation-rate products, but aren’t sure what to ask for. It’s not part of a customer’s daily life to be aware of all the various products and choices out there.
“So, we don’t say to homeowners, ‘Do you think you’d want rotating nozzles for this area?’ Instead, we guide them by saying ‘If you want healthy plant material in that bed without wasting water, here’s the type of product we recommend.’” Educate your customers by presenting them with all the options, explaining which ones are best for them, and why. Do a good enough job with that, and it should result in a sale.
Benson says most of her customers don’t initially know about the water-saving benefits of rotary nozzles. They just ask for them because they “look cool.” One of her customers had her install rotary nozzles because he wanted to be the first one on his block to have his sprinkler system “look like an amusement park.”
Low-precipitation-rate nozzles shouldn’t be a hard sell. Once your clients understand their benefits, they’ll be eager to jump on that E- ticket ride.