Why you will embrace subsurface irrigation’s water-saving efficiency
It’s easier to install a subsurface system before turfgrass sod is installed. Generally drip is put down in grid rows 12 to 18 inches apart and emitters spaced at about the same intervals.
Photos courtesy of Toro.
Business time is money. Many landscape contractors, and certainly property owners, are finding that water can be money, too.
With severe and prolonged drought encompassing certain parts of the country at almost any given time, more people are looking for irrigation options beyond the traditional rotors and sprays.
There are options available, of course. Landscape drip irrigation is increasingly making its way into planter beds and medians, although it has yet to truly sink its roots into turf applications.
Even with turf, subsurface drip irrigation is growing, and industry experts say drip in all its iterations is an idea whose time has come.
Getting a handle on numbers for landscape irrigation isn’t an easy matter, whether it’s trying to quantify water used, the number of drip installations, or even costs involved in those installations.
Mike Baron, national spec manager for water management products with Toro Irrigation based in Riverside, Calif., says one critical set of numbers involves the efficiency of different types of irrigation.
Efficiency is what counts
“An irrigation system comprised of rotors might be 70 percent efficient, while a conventional spray system might be 55 to 60 percent efficient,” he says. “However, dripline, installed at-grade and mulched over, is recognized to be at least 80 percent to 85 percent efficient, and subsurface drip is even higher; it’s recognized as being 90 percent to 95 percent efficient. That is providing the scheduling is done properly.”
And, not surprisingly, companies such as Toro are investing in innovative ways to make their overhead irrigation products more efficient. Baron says Toro’s Precision Series spray nozzle can deliver 70 percent efficiency.
That’s still not as high as the efficiency from even an at-grade drip system, and that’s the direction many landscape projects are taking, especially when it comes to decorative plantings.
“I’d say probably 80 percent to 90 percent of the dripline market is for planter beds,” says Mark Troche, director of sales and marketing for the landscape division of Fresno, Calif.-based Netafim USA. “We’re talking about a project where a contractor is putting it in the planters around a home, in multi-use family areas or commercial properties.”
Todd Polderman, product marketing manager for Hunter Industries in San Marcos, Calif., is even more specific. He says the most common use of dripline is for dense plantings such as hedgerows or groundcover.
“Using traditional dripline in subsurface turf applications is somewhat common in Texas in areas where legislation prohibits overhead irrigation in small areas adjacent to hardscape,” Polderman says.
Christine Canepa, senior product manager with the landscape drip division of Rain Bird in Azusa, Calif., agrees that for many people drip irrigation is primarily used for xeriscaping with subsurface applications being done under mulch.
Learn it first
One of the biggest drawbacks Canepa sees with using the technology under turf is lack of knowledge on how to properly install it. Toro’s Baron agrees.
“We hear from many contractors who are doing this for the first or second time, and they don’t take into consideration that there’s a learning curve,” Baron says. “There are a few who have made the strategic decision for their businesses to become experts and use it as a selling tool, but there are many others who get discouraged.”
While there is typically some additional labor involved in installing a subsurface system under turf (Baron estimates up to three times as much depending upon site conditions), he says those contractors also tend to drive those estimates up because of their inexperience.
However, the irrigation supply manufacturers are interested and eager to help their clients become more proficient at installing all kinds of landscape drip irrigation. For instance, Canepa says that his company offers an online design, application and installation manual that explains different types of dripline systems, as well as the drip products available through Rain Bird.
“The information is very available and very understandable,” says Canepa. “It helps a user determine the soil type, identify the proper flow rates and also the proper pressure regulation and filtration.”
If nothing else, she says it can be an aid for contractors wanting to educate their homeowner clients about the option of subsurface drip. Additionally, it provides grid layouts and a list of products that might be needed to install a system.
One of Rain Bird’s recommendations: an air-relief valve at the highest point in the system.
“One of the things most people aren’t familiar with is when you have a pressure-regulated dripline, when you turn a valve off, the vacuum that’s created can suck debris back into the line,” Canepa says. “You also want to have a flush point at the lowest spot in your system.”
A big concern for many contractors is whether they have a soil type that’s going to allow good lateral movement of the water underground. However, subsurface irrigation works in both sandy and clay soils because the goal is to get the water to move laterally, generally between grid rows that are 12 to 18 inches apart with emitters spaced at about the same intervals.
That’s not to say there aren’t challenges, however. Gravity tends to pull water down through porous sandy soils, while some clay soils don’t move water downward very well.
“You might decide that your run time should be one hour,” says Baron. “Few contractors will know that it is much better to pulse the delivery of the water during the day than to water for a full hour at a time during the night. Scheduling can definitely be an issue.”
Hunter Industries is so concerned about the soil’s ability to laterally move water that it’s developed a polypropylene fleece wrapping applied as part of an install called Eco-Mat.
“Eco-Mat succeeds where traditional dripline fails because it moves the water horizontally, regardless of the soil type,” says Hunter’s Polderman. “It holds the water at the plant’s roots, where it can be used more efficiently.”
Drip irrigation is particularly well-suited for watering containers and flowerbeds.
Photo courtesy of Rain Bird.
Not surprisingly, it’s easier to install a subsurface system under turf via new construction. However, it’s also possible to retrofit these capabilities, just as it is with dripline systems for planter beds.
Ideally, says Toro’s Baron, a retrofit would involve taking up the sod, leveling the area and installing the dripline grid before replacing the sod. The main advantage to that is the grid is all at one depth, eliminating the chance for an uneven application of water.
However, Netafim’s Troche says it is possible to do hand- or even machine-trenching 4 or 5 inches deep, then lay the tubing grid. He agrees that a uniform depth helps in getting good coverage, but says just as important for both new installs and retrofits is proper compaction of the soil.
“Again, if the compaction is even, it’s easier for the water to move laterally across the rows,” Troche says. “Some customers are afraid to compact because they think they’re going to crush the tubing. In fact, the tighter the soil, the better.”
Like Baron, he says the real secret to successful subsurface irrigation of turf is low pressures with multiple short applications of water spread throughout the day.
Perhaps the biggest problem with subsurface irrigation of turf is that both contractors and homeowners aren’t comfortable with the process because they don’t see anything happening.
“I think there’s a fear that if I don’t see the water running or I don’t see it thrown in the air then I don’t know if it’s working,” Troche says. “However, for most applications all the time we’re burying tubing anywhere from a couple inches to 6 inches below the dirt in planter beds, and it really is no different.”
And, Baron says there are solutions to that beyond blind faith, or increasing the watering times until the turf is swampy.
“We manufacturers have created different products to signal the gardener or contractor when the system is operating,” he says. “Toro offers a pop-up indicator that visually signals you when the system is operating.”
The real bottom line, these manufacturers say, is that more contractors are going to have to become familiar with dripline installations, more designers will be specifying them and more homeowners will be asking for them in the near future.
“We believe that subsurface irrigation will continue to grow in popularity because of the scarcity of irrigation water,” says Hunter’s Polderman. “The use of reclaimed and secondary water will also grow, along with wider acceptance of gray water, and gray water must be applied underground.”
Rain Bird’s Canepa believes people are already becoming more educated on the benefits of drip and many builders are moving to sell those benefits to them.
“Five years from now drip will be a generally accepted practice of irrigation, driven largely by the need to save water,” she says. “People are already recognizing it’s a more-efficient way to manage their landscapes.”
Troche is even more succinct: “I think it’s inevitable; how can it not be?”
K. Schipper is an experienced business writer who lives and works in Palm Springs, Calif. She is a partner in Word Mechanics. Contact her at [email protected].