The drive for increased irrigation efficiency has been a constant of the landscape industry for generations. This seems odd given that, compared to many countries, America is a land gifted with water abundance. The Great Lakes alone account for a fifth of the planet’s supply of fresh water. Still, the relentless growth of our population and the American dream of property ownership have combined to make wise water use a priority as well as a challenge.
To meet this challenge, irrigation contractors have stepped up to the plate. We use increasingly efficient sprinkler heads when designing more uniform irrigation systems. We propose rainwater harvesting and graywater reuse to our clients. With proper spacing, and the right heads, we can also create irrigation systems with high distribution uniformity (DU), an efficiency measure that only gets more important. Whenever a region, state or city makes decreasing water use a priority, we are happy to tell them how.
In turn, we rely on irrigation manufacturers to supply us with heads, piping and controllers that will keep our businesses running smoothly. They provide us with high quality, durable sprinklers, which are key to giving landscapes the right amount of water. Enough water that the plants thrive in the good times and survive the droughts, but not so much that water runs off, or drowns plants.
Sprinklers are generally classified by the range of area they cover, and at the top of the range for most commercial landscape contractors is the rotary sprinkler, or rotor. “Rotors range from 80 or 90 feet of throw at the top range for one-inch rotors, all the way down to 15 or 20 feet at the bottom range for half-inch rotors,” said Matthew Hall, Irritrol early product research manager.
Rotors are ideal for covering large areas, but there are a few things to keep in mind. The first is that, because they cover such large areas, they have much lower precipitation rates than spray heads, and will have to run longer to achieve the same effects. In areas where watering times are strictly limited, this can be an issue.
The second issue is pressure. We tend to think of rotors as requiring a lot of water, because they cover large areas, but Hall points out that sometimes rotors are good choices in cases where there’s less flow. “Let’s say you’re covering a small, rectangular lot with limited flow,” he said. “You could do square patterns with spray heads, but their precipitation rate will be very high. Instead, you can put rotors in that area, take better advantage of the limited water and throw farther than we could with spray heads, so it’s very site-specific.” The rotor will have to run longer, but if it covers all the plant material and the DU is higher, that’s a worthy trade.
At the top end of what a conventional spray head can reach, and the low end of what a rotor can do, is often an awkward radius that the rotating, or rotary nozzle was designed to cover. When affixed to a spray head, a rotating nozzle makes it throw like a multistream rotor, sending out multiple fingers of water in a turning, fan-like pattern instead of a flat, thumb-on-the-end-of-a-hose effect.
Rotating nozzles extend the reach of sprays, giving contractors the opportunity to achieve high DU ratings in otherwise difficult distances. Spray heads with rotating nozzles go up to 25 or 30 feet, and have lower precipitation rates, bringing the heads more in line with rotors. “Rotary nozzles are our most water-efficient products,” said Erica Bauman, operations director at K-Rain in Riviera Beach, Florida. The fan-like effect they produce is also a pretty visual, and some customers will ask for it, purely because of the aesthetic effect.
That’s not to say that rotating nozzles are without drawbacks. “They aren’t suitable for all types of environments, “said Bauman. “If a site has dirty water and no filtration, any nozzle will clog, I don’t care what they say.” The distribution uniformity of a system doesn’t really matter if it is so consistently blocked up that it hardly ever operates as expected.
Nozzles can be a hassle to change. While the radius can be adjusted by turning the breakup screw, it is a finicky business that can incur a steep cost to DU. Sprinkler companies have begun offering flow-control devices inside their heads to get around both of these issues.
“Flow control is a really great productivity tool that also saves water,” Bauman said. “On a head with flow control, you can adjust the distance and water flow proportionally, up to 30 percent, with just a flathead screwdriver.” Because the flow is adjusted at the head, DU is considerably less affected with this method.
When the area to be irrigated gets even smaller, spray heads, or sprays, are usually the preferred option. They are capable of throwing water up to 25 feet away, but their strength is in their small ranges; a spray head’s radius can drop to fewer than five feet. Some companies even offer sprays with rectangular patterns, designed to water side strips and the like.
Generally speaking, spray heads have higher precipitation rates than other types of sprinklers, so on large properties, they will probably be zoned separately from rotors or rotating nozzles. That way, by reducing the amount of time the spray zones are active, or setting up a cycle soak, you can keep them from overwatering the landscape.
While grass is the most common feature in both residential and commercial landscapes, it is not the only option, and landscape contractors must be prepared to care for other kinds of plant material as well.
Landscape beds and trees need water too, just not quite as much as grass, most of the time. While you may think their irrigation is handled through drip emitters or bubblers, it just isn’t so.
Bill Hutcheon, North American sales representative for Antelco in Longwood, Florida, explained the value of low-volume irrigation. “Most commercial heads discharge water at anywhere from three gallons per minute to maybe 50 gallons per minute,” he said. “Once the discharge rate drops below a half-gallon per minute, or 30 gallons per hour, it’s considered low-volume irrigation, and is usually exempt from water restrictions.”
These days, most modern sprinklers have stems that pop up when the system is running, but for low-volume irrigation, that isn’t always the case. “Micro spray is a spray head that has up to a seven-foot radius,” he said. “It’s on a small spike, it comes up through quarter-inch tubing, and it will cover a large section of landscape bed, so you don’t have to put a dripper at each plant.”
Water delivered via low-volume irrigation with micro- or mini-spray heads can also soak in more efficiently than water applied by larger spray heads. “Because you’re watering close to the ground, the water isn’t as likely to hit leaves and grass blades, so less water is evaporating,” said Samuel Thayer, president, Maxijet, Dundee, Florida. “You can cover the majority of the root zone really nicely with micro spray.”
When installing micro-spray heads, there are some guidelines to remember. Micro irrigation heads are more susceptible to debris in the water supplies than standard sprinklers. “If the water is coming in from a municipality, you usually don’t need filtration,” Thayer said. “But if it’s coming from a well system, you might want to use a filter on micro sprays, like 80 mesh screens.”
Micro irrigation also needs lower water pressure than the 40 or 45 pounds per square inch (psi) that standard sprinkler systems typically use. The ideal pressure ranges vary from manufacturer to manufacturer and from product to product, but 20 psi seems to be the accepted optimum pressure for micro spray applications.
In some cases, that pressure is reduced at the head. Not only does this make it easier to marry micro irrigation to a traditional sprinkler system, but it’s vital when planning the irrigation of a long landscape bed. A 300-foot run that only has 20 psi at the first head will not have enough pressure left after friction loss for the last head to function properly.
Controlling pressure isn’t just for micro-irrigation, according to Kelsey Jacquard, product manager at Hunter Industries in San Marcos, California. “There is definitely a trend towards pressure regulation at the head, whether it’s in spray bodies or even in rotors,” she said.
“Pressure regulation at the valve is fine for a small zone, but if you have a larger zone or the water is traveling a long distance, pressure regulation at the head allows you to have the same flow and even coverage out of each nozzle.”
Normally, if a head gets broken, all the water in the pipe starts flooding out, which robs the zone of pressure and can drown nearby plant material. There are devices that will slow or even stop the flow from a head in the event of nozzle removal, but most of these are placed in the middle or top of the stem. If the stem itself is snapped off by delinquent teenagers, absentminded mower operators, or oblivious drivers, the device will most likely go with it.
Pressure regulation that is found at the bottom of the stem is more likely to survive intact. Jessica Case, product manager for commercial spray heads at Rain Bird, said that the pressure regulation in their spray heads is designed to signal a problem as well. “The pressure regulator shoots a high indicator stream into the air at the same rate of flow as the nozzle,” she said. “So less water gets wasted, and the break can be spotted from further away.”
With more municipalities getting into water reuse every year, the water in a stream is less and less likely to be potable. Recycled or reclaimed water is a far cry from sewage, but you wouldn’t want to shower in it. It doesn’t meet the high federal standards for drinking water and by law, anything that carries it must be clearly marked, sprinkler heads included.
The nationally-recognized convention is to color anything that touches or carries reclaimed water purple. “That includes the heads, the valvebox lids, the pipes—anything that a customer might come into contact with,” Case said. “That is why some of our sprinkler heads come with purple wiper seals, for use with reclaimed water.”
We’ve hardly scratched the surface of the many design features found in commercial-grade sprinkler heads. Heads with check valves nullify the water pressure build-up from slopes, which causes sprinkler heads at the bottom of a hill to leak water after the system finishes watering. They also provide some protection from the water hammer effect, which can occur if the startup of an irrigation system goes too quickly.
Wiper blades limit the intrusion of debris into a head that results from the regular operation of a stem, while traps at the bottom of a head will collect any sediment that does get past. Some rotors now come with a few nozzles built directly into the heads; you can select the nozzle just as you would adjust the arc. Others can ‘remember’ their set arcs, and will automatically readjust themselves to cover those arcs, in the event that someone tries to mess with them.
Even now, there are novel approaches to sprinkler technology coming into the market. IrriGreen, based in Minneapolis, Minnesota, for example, offers a hi-tech head that ‘prints’ with water, shooting out 14 streams of water in a grid pattern from one side of the head. “You can program it to evenly water any shape within a 30-foot circle around the head, because the volume of each stream is proportional to the surface area.” said Ray Lamovec, the company’s sales and marketing director. “You don’t have to overwater 75 percent of a zone, just so the remaining 25 percent will be green.”
He sees it as a way for contractors to drastically reduce the number of heads needed to water an area.
“You’re actually gaining a lot of labor savings,” Lamovec continued, “because you don’t have to run laterals to all the edges of a zone. Instead of putting four, six or even eight heads around the edge of a lawn, where they are more likely to get damaged, you’re installing one head, right in the middle.”
It may seem like landscape irrigation is under fire these days, with all the water restrictions out there, and politicians calling for property owners to let their lawns go brown. These are, however, clear indicators of the pressure that water officials are under. That pressure can be a boon for your business if you’re willing to delve a little further into efficient irrigation methods.
Sprinkler heads are still the main method of irrigating properties across the nation, and manufacturers are tripping over themselves to make them more durable, more uniform, and in wider ranges. For landscape contractors who have irrigation in their revenue streams, the future is bright. Making a good sprinkler system function better might be a challenge, but with heads of all sizes, it’s a challenge we’ll be well equipped to meet.