The importance of efficient irrigation in landscape management grows day by day with many parts of the country being in extreme drought.
Another factor influencing turf and landscape watering is the hotly debated issue of climate change. While many scientists agree that climate change is underway, many people remain skeptical. What is unarguable, however, is the gradual creep northward of USDA Plant Hardiness Plant Zones.
Because the U.S. Environmental Protection Agency claims that turf and landscape irrigation accounts for 37 percent of U.S. freshwater usage, authorities in many regions of the country are seeking ways to reduce water use on turf and landscapes. For this reason, the efficient delivery of water through spray heads and rotors is critical for plant health and water conservation.
Irrigation spray heads and rotors have come a long way since the 1970s when the delivery of irrigation water relied primarily on the use of impact sprinklers. These sprinklers worked by using arms that swung back and forth to deflect water and dispense the water stream around in a pattern, explains Brent Barkley, Rain Bird product manager responsible for rotors, spray nozzles and spray bodies.
Rotors are gear-driven sprinklers that rotate, says Orion Goe, Toro product marketing manager. They can deliver water in a full or semicircle as required and set by the user. The most widely used rotors typically “throw” water an average distance or radius of 30 to 40 feet. The distance is dependent on rotor size and water pressure so the range can be anywhere from 22 feet to more than 100 feet, he adds.
Rotor-type sprinklers are found in a variety of medium- to large-size residential and commercial turf irrigation applications, such as golf courses, sports fields, public parks and green spaces.
“When compared to spray heads, some advantages of rotors are their longer radius capability, which means fewer heads—or individual sprinklers—needed to be used to cover a specific area,” Goe adds. Their larger nozzle openings tend to clog less often, and they typically allow more adjustability than spray heads that may have fixed arcs and/or radii, he adds.
“However, some disadvantages are seen in lower precipitation rates than spray heads as a result of their rotation, and rotors do not adequately address radius requirements of less than 20 feet,” Goe says. Distinguishing features of rotors include check valves, slip clutches, interchangeable nozzles, tool-free arc adjustments, pressure- activated wiper seals and MPR radius reduction, he adds, explaining that rotors are often classified by their radius and GPM flow capabilities.
Spray head features
Spray heads feature pop-up stems and risers, typically fitted with fixed spray or rotating stream nozzles, says Goe. Spray heads are available in various configurations, stem heights and features, such as in-stem pressure regulation, check valves and automatic flow shutoffs.
“Compared to rotors, spray heads are typically found in smaller areas, namely residential yards and gardens, medians and small- to medium-sized commercial settings,” Goe says. “A spray head is accented by the nozzle, and, when combined, the two serve to meet the irrigation needs of the design.”
Spray head irrigation nozzles are available in a variety of patterns or arcs, from one-quarter to full circle, with distances ranging from 4 to 15 feet.
“However, odd arcs, such as 60 degrees, 120 degrees and 240 degrees, as well as side strip arc patterns, are growing in popularity as contractors and homeowners are becoming more water-conscious and working to ensure water is being used as intended and overspray is eliminated,” Goe says.
Spray heads and fixed nozzles allow more flexibility in irrigation design over rotors, Goe notes. “Higher precipitation rates allow shorter watering times. Nozzle replacement and servicing is typically easier and more cost-effective,” he says. “Some disadvantages are seen in their propensity to clog due to smaller orifices, high-end radii of 15 to 18 feet of spray nozzles, and comparatively very high precipitation rates of variable arc nozzles and legacy spray nozzles.”
High-distribution uniformity is a key feature of spray heads and spray nozzles, Barkley notes, adding sprays with basic nozzles can be the most cost-effective and present flexibility through numerous options. “Variable arc sprays allow you to have fewer individual nozzles to stock, allowing you to use one nozzle for many different applications and adjust that to the application you need,” he says. Many contractors derive better distribution uniformity with fixed sprays, he adds.
“They like that there is a fixed pattern that can’t get out of whack over time or be vandalized,” Barkley continues. “Those fall in the classification of standard precipitation nozzles. They are good for applications where there is no slope or the soil has a quick infiltration rate.”
Rotary nozzles are a relatively new class of nozzles, says Barkley. “Those are low-precipitation nozzles and are very good for slopes or soils with a slow infiltration rate like clays,” he adds. “They apply the water at a much slower rate, so there is no run-off. They also have great distribution uniformity and can be very efficient users of water.”
Another classification of nozzles is high-efficiency nozzles. “They would be on a standard precipitation side, but they’ve been engineered to have a higher distribution uniformity for better efficiency in spreading water,” Barkley says.
Drip irrigation is emerging as a complementary irrigation product that targets areas difficult to irrigate with sprays and rotors and offers strong efficiency advantages, adds Barkley.
Preferences depend on application
Contractor preferences vary, Barkley says. “Many contractors prefer to use variable arc nozzles because they want to use only a few nozzles for any application,” he says. “Many prefer fixed nozzles because they perceive them as having better distribution uniformity. They don’t have to worry about adjusting them—they simply install the ones they need in the right locations.”
Many contractors have been able to upsell customers to more high-efficiency systems and are targeting the high-efficiency nozzles, which may come in fixed, variable arc and rotary designs, says Barkley.
“All contractors may choose to use rotary nozzles when they’re looking for a low-precipitation application,” he continues. “Also, it’s sometimes driven by customer preference. There’s an aesthetic value to the rotary nozzles that has emerged in the last several years. They simply look very nice on the property and that drives contractors to use them.”
The popularity of rotors versus spray heads depends on the application, Barkley points out. Turf size plays a role in the choice.
“Markets like Southern California tend to use a lot of sprays and relatively fewer rotors,” he says. “Areas like the Midwest, where lawns tend to be larger, tend to use a ton of rotors and still use sprays, but proportionately fewer.”
As both rotors and spray heads have their unique strengths for particular applications, it is difficult to draw conclusions around which are more popular, notes Goe.
“There are definite trends emerging when it comes to fixed nozzles as we are seeing high-efficiency fixed spray and rotating stream nozzles increasing in popularity given their low-precipitation rates and ease of use,” he says.
Specifiers and contractors are placing more emphasis on water-efficient products that yield a double benefit: effective water use resulting in efficiencies and end users’ resulting lower water bills.
Cost and product lifespan
The design life of spray heads, nozzles and rotors is at least five years, Barkley says.
Depending on the manufacturer and features, spray heads and bodies can range from $2 to $12. Higher-priced products may offer durability for use of reclaimed water, which may contain chlorine, grit and debris. They also may have built-in pressure regulation to reduce misting and fogging, a check valve preventing low head drainage and flow control, which can choke off the flow of water in case the nozzle head gets knocked off.
A residential/light commercial rotor may retail from $12 to more than $100. Higher-priced rotors are designed for such applications as sports field irrigation and may have stainless steel construction and other specialty features. Features may include a built-in check valve, pressure regulation, nonpotable reclaimed water markings, stainless steel options for vandalism protection and more stem durability.
Rotary nozzles, which range from $1 to $8, tend to be more expensive because they cover a larger area and have more built-in technology, Barkley points out.
How to choose
Durability, ease of installation and efficiency are important factors in choosing the most appropriate rotor or spray head for a particular irrigation project, says Barkley. “That may mean choosing a variety of options and features, depending on the installation,” he says. For example, an application with large changes in elevation may call for installing a check valve to avoid a lot of low head drainage.
In a reclaimed water situation, contractors should seek rotors offering reclaimed water indications. The same holds true for spray heads, Barkley says.
“Standard precipitation versus low precipitation would be one of the first factors a contractor should consider,” he continues. “If it’s a need for low precipitation, then they may want to select a rotary-type nozzle. If it’s not low precipitation, then certainly other nozzles would work. Standard precipitation nozzles will work and oftentimes cost less money than the rotary style.”
The market also dictates choices, such as whether homeowners are more responsive to higher-end systems that have higher efficiency, which, if installed and maintained correctly, should conserve more water and reduce the system’s operational cost, Barkley points out.
If they haven’t seen the product in action, contractors can make the best decision by reading trade journals that outline product benefits, which also are featured on manufactures’ websites. Distributors also are good information sources, Barkley says.
Going forward, look for manufacturers to design rotors and spray heads offering contractors and end users continued ease, performance, durability, water efficiencies, pressure regulation, versatility and distribution uniformity improvements.
Standards released by the American Society of Agricultural and Biological Engineers will “champion further publication of distribution uniformity for manufacturers’ products,” notes Barkley. “That is going to raise the visibility of that distribution uniformity, as well as precipitation rates, for all products, spray nozzles and rotors included.”