Drip Irrigation

MARY ELIZABETH WILLIAMS-VILLANO | Drip Irrigation - Low Flow
It’s a thirsty world out there, and it’s only getting thirstier. Experts are telling us that with climate changes, we can expect more drought, not less.

So where does that leave landscape and irrigation contractors? As more water agencies push for less watering on landscapes, and customers start complaining about their increased water bills, they will demand that lower amounts of water be delivered with greater efficiency. Smart contractors will increasingly be turning to drip irrigation.

“Drip irrigation is getting bigger,” said Stuart M. Spaulding, a CLIA (certified landscape irrigation auditor), and customer and technical service manager at DIG Corporation in Vista, California. “One reason is that the cost of water keeps going up.”

“With the heat here in Arizona, the evaporation rate is tremendous,” said John Gary, irrigation specialist at Tucson-based Horticulture Unlimited, Inc. “Putting pointsource emitters right on root zones is not only more efficient, it prevents weeds and other unwanted plants from sprouting up in the areas between the plant material.”

“Drip irrigation has been growing at least twice as fast as the market at large over the past several years,” said Todd Polderman, product marketing manager at San Marcos, California-based Hunter Industries.

“This will only continue to accelerate as water becomes scarcer, particularly in areas where population growth is outstripping infrastructure, and in areas where they’re starved for water, like Texas.”

Some people are discovering drip because they’re being forced to, particularly in the West, where drought has been a major issue. In California, Assembly Bill 1881 prohibits overhead irrigation within four feet of non-porous hardscape on new installations; Texas has similar legislation. Other municipalities throughout the country have enacted or will enact ordinances like it.

“We’re definitely seeing legislative influence mandating the continued, increased use of water-efficient products and drip irrigation,” said Polderman. A lot of water districts are making rebates available for conversion to drip systems, and making those systems exempt from restrictions such as odd/even watering days.

“Drought is driving regulations, which then drives the market,” said Mauricio Troche, director of sales and marketing, landscape and turf division for Fresno, California-based Netafim, USA. “People hear the news, then take the initiative to have drip irrigation installed.”

Drip systems conserve water because they apply water directly to the root zones of plants. “Very little, if any, is lost to runoff or evaporation, because you’re not throwing it up into the air,” said Spaulding. “Conventional sprinkler systems are about 55 percent efficient. But drip irrigation is 90 percent efficient.” In general, drip irrigation systems cut water usage anywhere from 30 to 50 percent.

Troche says the commercial and residential sectors are growing equally fast for drip. “The popularity is also being driven by landscape architects. As stewards of the land, landscape contractors and landscape architects are really into conserving water.”

Drip irrigation components consist mainly of poly tubing, low-flow valves, filters and regulators, and emitters that release water slowly. Some dripline is sold with emitters already inside the tubing. Emitters come in a variety of flow rates, typically 0.26, 0.4, 0.5 and 0.9 gph (gallons per hour).

The tubing can be laid on grade and stapled in place every three to five feet, and buried under a few inches of mulch, or staked a few inches above grade, as is often done in landscape beds. Subsurface drip systems are completely buried, usually anywhere from four to six inches deep.

It’s all about the soil

Water’s relationship with soil is critical to the success of any drip irrigation installation. Before you do anything else, you’ll need to determine the type of soil you’re dealing with—clay, sand, or loam. This can make or break a project, because different soil types have different field saturation rates. That’s the technical term for the maximum amount of water that soil can absorb; anything over that is runoff. Emitters come with set flow rates, so you’ll need to know this before you decide which ones to buy.

“I’ve seen soils that vary widely in different parts of the country and even in the same city,” said Gary. Soil variance is immense, and every site’s different.

“Drip irrigation puts water down slowly, but if you have heavy clay soil, it will become saturated and start to pool,” said Jeff Chaffee, director of operations at Master Landscape, Inc., in Manhattan, Kansas.

“Or, if you have really sandy soil, the water will tend to drain away quickly. You have to watch that when you’re programming a controller, telling it how often or how long you want the system to run.” To avoid that problem, he recommends adding soil amendments before installing a drip system.

Ken Barthuly, vice president and co-owner of Zionsville, Indianabased Barthuly Irrigation, Inc., can tell you firsthand just how critical soil type is. His company was hired by a school district to install subsurface drip on an athletic field, the first time this had ever been done in the Midwest.

“Here in Indiana, we have hard clay—we call it ‘hard pan,’” said Barthuly. “So, the landscape architect specified that an eight-inch layer of PGA soil be used to overlay the tubing. PGA is a type of soil mix that the Professional Golf Association recommends, a blend of sand, soil and compost that allows for the proper wicking of water into turf. The drip emitters themselves were supposed to lie on top of the hard-pan clay, under this thick layer of PGA soil.”

However, the PGA soil was applied unevenly by another contractor. “We weren’t supposed to hit hard pan until we went down eight inches. But in some places, we hit hard pan after only two inches. Now, all of a sudden, our pipe is not at exactly eight inches, and in some sections, it’s in clay, not in the PGA mix.”

“Water doesn’t wick up as easily in that hard pan, so we got a lot of puddling and things like that.” Some spots got too much water, and some not enough, leaving brown patches.

However, the project saves a considerable amount of water for the school district. Because of that, subsurface drip for athletic fields is becoming more and more common.

Maintenance

All irrigation systems require maintenance, and drip is no different. “We tell people to flush their drip systems out once or twice a year, in the spring and the fall. This will get out any type of mineral buildup or anything else in both the filters and the pipes,” says Gary. “Also, the pressure regulators need to be checked, to make sure they’re not plugged up with debris.”

“Emitters can plug up with grass roots,” he continued. “Some companies put copper inlays in the emitters, to help keep the roots from growing into the lines. Another company has a root killer, an herbicide, impregnated into the plastic by the emitter, but after a period of time, it will fade out. Eventually, the roots will get inside.”

The wild kingdom is another wild card. “Out here, we have a lot of critters—javelinas, coyotes, bobcats, and rabbits,” Gary said. “They’re not dumb. If the tubing is staked up out of the ground, they’ll find it and chew on it, because they know there’s moisture there.”

Gary saw this with his own system. “One early morning, I saw a line of evenly spaced rabbits, each one so many feet apart, waiting. I wondered what was going on. Then I realized that at 6:00 a.m., my drip irrigation system was set to come on. Each rabbit was stationed next to an emitter, waiting for the water to come out. They had learned the timing!”

Fangs aren’t the only things that poke holes in tubing. You need to make sure subsurface drip tubing is buried deep enough down, at least five inches, so that anyone aerating the soil later on won’t puncture it.

How does above-ground drip tubing stand up to all that bright Arizona sun beating down on it? “The UV light will start breaking down the poly in the tubing, and it will start becoming brittle and break,” says Gary.

“So we bury it two to four inches underground, then put rock mulch on top of the soil. It looks a lot better, too, because the tubing’s usually black, so it’s very obvious when it’s above ground. As long as the tubing is kept out of the UV light, it works beautifully, and lasts several years.”

Selling it

Drip irrigation is an easier sell when the weather helps you out. Not surprisingly, Gary says drip is very popular in Arizona.

“We’ve been doing drip irrigation for 25 years, mostly for residential clients,” says Chaffee. “A good chunk of our systems are exclusively drip, and it’s rare to see a system that doesn’t incorporate drip in some way. It’s pretty well-accepted around here, so it’s not a hard sell for us.”

Customers ask for it and are usually fairly well-informed about its advantages. “On the other hand, we work really hard telling them the reasons why drip irrigation is a good choice.”

“Drip goes over well,” says Chaffee, despite the fact that Manhattan, Kansas, hasn’t had any water restrictions. “I’ve been living and working here for more than 20 years, and I’ve never seen any water restrictions,” he said. “But there are some towns nearby where that’s been a problem. I know a couple of landscape company owners in those towns, and they’ve said it makes drip an even easier sell.”

Cost factor Drip systems, especially subsurface ones, are usually a bit more expensive to install than conventional irrigation systems—but not always. “For us, it’s probably about a wash,” said Chaffee. “In certain circumstances, it may be slightly more; in certain others, it may even be cheaper. In the long run, the customer is going to be saving on their water bills.”

“If you compare the cost of drip tubing to the cost of six or seven sprinklers and the hard piping and larger valves that go with that, the cost of the products is less expensive,” says Troche. “You’re also using a smaller controller and not as many items as with a conventional system.” Labor is usually the factor that drives a drip system price higher.

For cost-conscious customers who already have a conventional system in place, retrofitting may be the way to go. “It’s easy to convert from conventional irrigation to surface or subsurface drip, depending on the size of the installation,” says Troche. “All you have to do is cap off the sprinkler heads. All the irrigation companies make caps for their sprinklers. You unscrew the old sprinkler heads and cap all but one of them. Then, you put a retrofit kit with a filter regulator on that old stem and run some tubing out from it—about 12 to 18 inches apart—depending on your soil and plant types.”

A subsurface drip system can even be retrofitted without ripping out an entire lawn. “You can just cut into the lawn about every 12 to 18 inches with a trenching tool, drop in a line of tubing, then compact the dirt back down in the trenches,” says Troche. Retrofitting works well as long as the trenches are compacted down tightly; loose soil won’t transport water correctly.

William Trudeau, owner and president of Upland, California-based Tru Landscape Design, Inc., installs a lot of drip systems in just that way, for customers who initially wanted to save water by taking out turf. He tells them it will cost less, about $1.50 per square foot, for him to retrofit their turf with trenched-in subsurface drip than to come in with a sod cutter and remove it. “At the end of the day, turf removal would cost the customer about $3 per square foot, once I put in the new plant material.”

Right for turf?

Many irrigation professionals think that the technology for subsurface drip isn’t really “there” yet, especially when it comes to turf. “If I’ve ever said that, I want to amend that now,” said Spaulding. “There have been really significant advancements in the technology of subsurface drip irrigation, in both driplines and emitters, even since last year. A lot of the old problems that used to plague subsurface systems, such as root intrusion and poor uniformity, are getting minimized now, if manufacturer recommendations are followed.”

Troche agrees. “When contractors say the technology for subsurface drip isn’t really there, that it can’t work, or that it’s hard to do maintenance on, that’s really just a perception, and it’s up to us, as manufacturers, to continue our training efforts. You can install subsurface drip on turf and be very successful. There are some irrigation contractors who exclusively install subsurface drip all over the country, in cold and warm climates. The fact that these contractors are as successful as they are shows that it works.”

The technology has come a long way. To discourage root invasion, some driplines now have physical barriers, copper inlays or optional filters implanted with herbicide. Better screens and disc filters keep lines and emitters from clogging. Check valves and anti-siphoning devices keep dirt and water from getting vacuum-sucked back into emitters.

Troche thinks the concern about roots getting into drip systems is overblown. “Whether it’s in landscape or agriculture, with the millions of feet of tubing we sell every year, we really don’t get it coming back to us because roots have gotten in there.”

Now is the time to get drip-savvy, if you’re not already. “There’s going to come a day when people will be removing 30 to 40 percent of their turf,” says Trudeau. “When that day comes, the contractors that have put in the time to understand drip are going to be busy, very busy.” Why not be one of them?

 
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