Can You Do Drip?
When it comes to landscape irrigation, the future is all about efficiency. Droughts are more prevalent than ever, and the national population never stops growing. As a result, state and federal governments—as well as the public at large— are becoming more aware of how we use water, and how much water goes to irrigating landscapes.
The continued success of the green industry relies on using more efficient methods to reduce how heavily irrigation weighs on the potable water supply. One of the most efficient methods out there is drip irrigation, so let’s take a quick look at what goes into a drip irrigation system, and how drip is evolving.
First, some drip anatomy. “A drip irrigation system starts with a control-zone kit, which consists of a valve, filter and pressure regulator, and then some sort of water transport, be it PVC or polyethylene tubing,” explained Janet Reilly, director of the drip landscape division for Rain Bird in Azusa, California. A number of lateral lines are attached to a single line, through headers, and the laterals are then fitted with emitters to disperse water.
With that in mind, what do you picture when you think of drip? Is it a landscape bed, with tubing running from one plant to another? Drip irrigation can also be a series of tubes running under a grass lawn, or buried under a landscape bed, or ringing a tree. Drip systems can support bubblers and micro sprays, and they aren’t just for the arid Southwest.
America is a big country, with a growing population, and there’s always a drought happening somewhere. When lawmakers are looking to conserve water, especially during a drought emergency, they always target landscape irrigation first, because it comprises 30 to 50 percent of household water usage. They put water restrictions in place, to limit how often irrigation can be used and for how long.
Some states suffer droughts quite often, and their legislators have more experience with it. In these places, water restrictions often exempt irrigation that uses 30 gallons per hour or less. However, in states where droughts are a rarity, the existing rules for water restrictions may be outdated, and may not take drip irrigation into account.
That’s apparently the case in Massachusetts, where Tim Preston is the irrigation manager for Wisteria & Rose, a Boston land care company. “The big push in Massachusetts right now is to get drip irrigation excluded from drought restrictions,” he said. He’s a big believer in the power of drip irrigation. “Drip eliminates waste, because any excess water just recharges the groundwater.”
Preston can’t afford to have any runoff, because many of his projects are container plantings that use a limited amount of dirt. He specializes in using drip irrigation for courtyard and rooftop installations, to prevent water from overflowing these areas.
However, Preston says that contractors learning about drip often make the opposite mistake, and don’t apply enough water. “When landscape contractors who are used to doing lawns suddenly start installing drip irrigation, they generally don’t run it as long as it needs to be run.”
If you’re used to calculating in gallons per hour, it can be easy to get confused about how much water is actually reaching root zones. In a well-designed sprinkler system, the sprinkler heads are throwing water at thirsty plants. Some of that water will fall directly on the ground, where it will soak right in. However, even the best sprinkler system loses a significant percentage of water to evapotranspiration. Accounting for the difference is a matter of experience, according to Preston.
A.J. Downs, operations manager for Landscaping One, Inc. in Cumming, Georgia, has that experience.
He prefers to use drip irrigation whenever possible on landscape beds. “When I’m planning a system, I’m thinking first about whether I want to use point-source or inline tubing,” he said.
Point-source is the most customizable form of drip. You lay out your tubing, and then install emitters wherever they are needed along its length. “Point source is great to use when there are a number of plants with different watering needs, or it’s unevenly spaced,” said Reilly. “It is very precise.”
That’s because when you’re installing point-source irrigation, you can customize emitters with a variety of different aperture sizes, along with the spacing of your emitters, to accommodate different watering needs in the same zone. A succulent might get one small emitter, while the thirsty plant further down the line might get three or four large emitters.
Inline tubing comes with the emitters pre-installed at set intervals of 6, 12, 18 or 24 inches. It isn’t as customizable, but it cuts down on labor costs in some areas. “Say you’ve got a long hedge, where the plants are two or three feet apart, it makes sense to water that area with inline tubing,” said Downs.
Convenience isn’t the only advantage, either. “All the plants are going to be close together in a line, so it’s a little bit faster,” he said. “Plus, you know you’re going to water that whole area, so you’ll put it right on the roots and all the roots are going to grow together. If they were four or five feet apart, you wouldn’t want to use inline.” With spacing that wide, some of the emitters would not reach the plants.
Just as sprinkler-based irrigation systems are more than just heads and piping, drip irrigation systems are more than just emitters and tubing. Because drip systems are more sensitive to clogging than sprinklers, they are more likely to need filtration, even when using municipal water.
The filters need to be cleaned periodically, though how often depends on the quality of the local water and how often the irrigation system runs. “We recommend putting some type of flush device at the end of every line, so that every time the system comes on, it is filtered and then flushed at the end,” said Richard Restuccia, vice president of landscape solutions for Jain Irrigation in Ontario, California. If the local water has a lot of silt and sand in it, there are self-cleaning filters on the market that will flush out the material automatically.
The key is to get a filter that fits your area’s needs. “In most cases, a 100-mesh to a 150-mesh screen will be a fine enough filter for a drip irrigation system,” Restuccia said.
“There are some places, in Colorado for example, that have very silty water and need better filtration than that.”
Pressure regulation is also important for drip systems. The fittings in a drip system are often rated for a maximum of 50 pounds per square inch (psi), although most manufacturers recommend a maximum of 40 psi. If the water pressure is ramped up, fittings can be clamped in place to keep them from popping off under pressure, but once the psi rises high enough, the emitters will start popping off of the line.
When you’re installing an irrigation system that’s all drip, pressure reduction can be taken care of right at the start. But in many cases, drip irrigation and sprinklers coexist in separate zones on the same system. “When you’re retrofitting an existing system, you can put a pressurereducing valve right at the spot where you’re tapping into your existing system in the field,” said Restuccia.
Retrofitting is a popular option when property owners are looking to increase their water efficiency without the expense of overhauling their entire irrigation systems. The process usually starts with capping off the spray heads around a landscape bed, and installing a pressure-reducing valve and a filtration unit at the start of the zone. Then, the lateral driplines can be run straight from the existing pipes. Retrofit kits are also available, which include filtration and pressure regulation in a spray body.
Just like sprinkler systems, drip irrigation systems need to be adjusted to account for plant growth.
However, instead of changing the arcs of sprinkler heads, you’re moving laterals to account for new root circumferences. “Sometimes, with point-source drip irrigation, y o u don’t even need to do that,” said R eilly. “R ather than change the product, you can just change the watering times, or add more emitters to a section of line.”
Once clients see how efficient drip is for the magnolia grandiflora or the muhlenbergia capillaris in their landscape beds, they may be willing to convert their lawns over to drip as well. Subsurface drip irrigation, or SDI, has been around for decades in agriculture, but until recently, it was hardly used in landscape irrigation at all.
Thanks to increased public interest, largely driven by the droughts of recent years, subsurface drip installations for lawns have really taken off. This has also been partly fueled by new technologies that reduce the clogging problem that SDI systems are prone to.
SDI systems have always had to fight clogging on two fronts: clogging from within, by insufficiently filtered water, and clogging from without, by plants sending their roots directly into the emitters. A plant thinks a drip emitter is a new underground stream, and tries to tap it directly. Without any method of preventing root intrusion, SDI systems would eventually clog, and only water the plants that had managed to tap the emitters.
Now, emitters will come implanted with herbicides or embedded with copper, to keep roots from directly entering the line, so root intrusion is less of a problem. Installation costs have also gone down, as manufacturers have responded to the new market. Some sell tubing with pre-spaced headers for the lateral lines built right in, or even entire drip system kits, which include filtration and pressure reduction.
Downs, who emphasized the importance of using high-quality materials, likes to use these plug-and-play kits. “They make it easy and straightforward,” he says. “Then, you can just put the water right where you want it, with either point-source or inline tubing.”
When water is going right to the roots, it isn’t staying on the leaves of delicate plants like roses. Water on the leaves of plants encourages the growth of fungal diseases like rose rust, which is a maintenance nightmare. You save on fungicides, the time/cost of nursing sick plants, and in the worst-case scenario, replacing dead ones.
While driplines are carrying water around a property, they can be carrying fertilizer as well. Fertigation units automatically inject liquid fertilizer into irrigation systems, and they tend to mesh well with drip technology. “They’re starting to catch on now,” said Restuccia. “I think that contractors are seeing the benefits. They’re saving time, they’re saving their customers some money, and most importantly, they never need to water-in fertilizer, so they’re saving some water, too.”
Saving water is what drip irrigation is all about. Restuccia estimates that drip systems use a little more than 50 percent of the water that sprinklers use. In the best-case scenario, clients will see their water bills drop 25 percent overnight. With installation costs dropping, and water rates rising in regions across the country, drip irrigation is becoming a smart financial investment, as well as a waterwise one.
Take Georgia, for example, which has been in drought for a little over a year now. At the time of this writing, 12 counties in Georgia are at level-two drought restrictions, and 43 counties are at level-one. Downs expects that if his county hits level three restrictions, public awareness of drip irrigation will grow significantly.
“I don’t think a lot of people are privy to it right now, but as soon as they start getting fines, and regulations are imposed, that’s when more people are going to want to come forward and get something they can use,” he said. “People can’t stand having an irrigation system and not being able to use it.”
That, more than anything, is why drip is important to the future of the green industry. As a nation, we have a limited supply of fresh water, and a steadily growing population. We store water in reservoirs, run it through hydroelectric dams for power, and grow crops with it. Water is vital to many industries, not just our own, but with the starring role that irrigation plays in household water usage, it is a prime target for conservation efforts.
There are other efforts being made to ensure that there is enough water for everyone. Cities are beginning to provide non-potable water for use in the landscape. Research into cheaper, more effective water filtration technology is making desalination of seawater and brackish water more feasible. There may even come a day when it is illegal to use drinking water for irrigation.
The green industry has thrived for decades because it represents a cornerstone of the American dream, a piece of land to call your own. Now our country is concerned with making that dream sustainable, with balancing our personal and societal goals with the natural resources they require.
Drip irrigation addresses that concern beautifully.
It lets property owners have their cake and eat it, too. Sprinkler systems are going to be around for a long time to come, but drip may be going mainstream if the current trends in water use continue. Contractors who are well-versed in its idiosyncrasies will have a bright future ahead of them.