Is Drip and Low-Flow the Future of Landscape Irrigation?
15 June

Is Drip and Low-Flow the Future of Landscape Irrigation?

There’s so much media coverage on the topic, you’d think that the entire planet is turning into one big sand dune. That’s a bit of an exaggeration, of course. Nonetheless, all kinds of smart people all over the globe are predicting water shortages and continued periods of drought over the next thirty years, and probably beyond.

Whether you blame politics, the population explosion, climate change, or thirsty aliens from outer space, the reasons don’t really matter. What does matter is that the need to conserve water isn’t going to go away.

What does this mean for irrigation contractors? It means that anything that decreases our use and especially our overuse of water is going to keep getting a higher and higher profile. One of the most, if not the most, efficient means of delivering water to plant material is drip and low-volume irrigation. The argument can be made that it is the future of irrigation.

The typical water savings with drip and low-volume irrigation ranges anywhere from 30 to 70 percent. That’s true of both commercial and residential applications.

What do we mean by ‘drip’ and ‘low-volume?’ The terms are often used interchangeably, but they’re not quite the same. Drip is subsumed under the category of low-volume. It uses plastic tubing with emitters embedded inside. The tubing can be laid directly on the ground, under a layer of mulch, or buried six inches down. Then, it’s called subsurface drip irrigation.

A low-volume system is defined as one that delivers from 30 gallons per hour (gph) to as low as 0.5 gph. Water is seeped slowly at or near plant root zones. Virtually none is lost to evaporation.

By contrast, flow rates from traditional overhead irrigation sprays and rotors are always measured in gallons per minute (gpm). Rotors can range from 60 to 600 gpm.

Micro sprinklers, micro sprays and micro bubblers, connected by flexible tubing staked above ground, are also part of low-volume irrigation. These are usually used for denser groups of plants, such as shrub beds.

It’s getting more popular 

“It’s been growing a lot over the last two years,” confirms Peter Lackner, product manager for landscape drip at The Toro Company’s Riverside, California-based irrigation division. “That’s not confidential information; anybody would tell you the same thing.”

The company has seen that growth happening, and not just in drought-stricken California. “Of course, drought increases the popularity of drip because it’s so much more efficient. But anywhere that water is in short supply or is more expensive, drip is definitely a big part of the conversation.”

“Drip and low-flow applications are very early in their adoption lifecycles,” said Rick Foster, marketing and sales manager for the landscape drip division of Rain Bird Corporation in Azusa, California.

“It’s been very popular in regions such as Southern California and Texas, where drought conditions exist. But it’s becoming equally important in other regions, even in places that are regularly buried under several feet of snow, such as the Northeast, where drought’s not as severe or is nonexistent.”

The rapid growth is being driven by drought, population increase and the rising cost of water, says Foster, who expects this growth to continue for many years. In commercial applications, developers desirous of LEED points will turn to drip and low-volume for a least some of a project’s irrigation needs. Increasingly, drip and low-flow is being mandated for new development.

Judith Benson, president and owner of Winter Springs, Florida-based Clearwater PSI, Inc., started doing irrigation 18 years ago. Back then, when she talked to developers of new construction, there was no inline drip or micro irrigation being used or discussed. “Everybody was still using sprays or rotors. Now we’re seeing much more low-flow and inline drip in those commercial installations.”

It’s even getting more popular in turf applications. “Subsurface drip irrigation under turf is rapidly becoming a larger sector of the market, and we’ve been doing it for many years with great results,” said Mauricio Troche, director of landscape at Netafim USA, Fresno, California.

It’s more efficient 

There’s no question, really, that drip and low-flow irrigation is a much more efficient way of delivering water to growing things than conventional sprays or rotors. The only question is how much more efficient it is.

Stacy Gardner, project manager for Pepperell, Massachusetts-based Irrigation Consultants, Inc., says that drip irrigation delivers the highest efficiency of any type of irrigation system, usually around 90 percent.

“Water delivered by traditional overhead irrigation sprays and rotors is always measured in gallons per minute,” says Rick Foster. “In drip and low-volume, we live in the world of gallons per hour. Rotary nozzles and high-efficiency nozzles can overlap into the gallons-per-hour scale, with some delivering as low as 20 gph.”

Drip is increasingly being driven by legislation 

Increasingly, drip and low-volume irrigation is being specified as a matter of law.

Robert Maxvill, owner and president of Aquamax Sprinkler Systems, Inc., Dallas, Texas, says that drip is much more predominant now in Texas, as it’s starting to be required in areas where it wasn’t before. According to state regulations, you must use drip irrigation in flowerbeds and on parkways less than 48 inches wide. Some cities go further than that, with stipulations that any area less than 60 inches wide must have drip.

“A lot of cities are tending to use more drip, because of the water efficiency and the fact that, in Texas, with our drought situation, each city is restricted as to how many days a week they can water. That changes depending on the lake level, so it can be anywhere from a couple times a week up to once a month.”

Maxvill adds that drip irrigation systems aren’t subject to watering restrictions. Being able to water any hour of the day, seven days a week, pushes more people towards drip.

“Texas has been active with legislation, because of their drought,” says Foster. “The city of McKinney recently mandated that you can only irrigate every two weeks, but drip is completely exempt from that.” To be exempt, an irrigation zone must be irrigated solely by drip, not by a mix of sprays and drip.

Foster says this is stimulating the adoption of drip. “If folks know they’ve got an exemption, they’re more likely to install it in a new home or retrofit an existing zone. The 1881 rule (California law AB 1881) prohibits overspray that you get from traditional irrigation systems. As a result, many homes in California are being installed with systems that are 100 percent drip, due to that legislation.”

There are other incentives for property owners out there as well. “‘Cash for grass’ programs are growing,” said Troche. “I’ve seen anywhere from one to four dollars per square foot being paid out for removing turf and replacing it with drought-tolerant plants and drip irrigation.”

Retrofitting is easy

It’s not that difficult to convert a conventional irrigation system to drip. “All it takes is one fitting to connect a drip hose up to PVC pipe where a sprinkler might otherwise be,” says Lackner. “Then you’re off and running.”

And it’s fairly cheap to do. Lackner says the actual pieces required to convert a system are very inexpensive. He admits, however, that the overall installation cost is possibly a little bit higher than conventional systems up front, simply because of the need to run tubing across an entire area, versus putting sprinklers around a perimeter.

However, the payback is quick due to the greater efficiency. The more expensive the water is, the faster the return on investment will be.

Drip and low-flow systems can be retrofitted easily in landscape or shrub beds, either with tubing laid on top of the ground, under a layer of mulch, or buried under topsoil. Micro sprinklers and micro emitters are staked above ground, just as easily.

But what about under existing sod? Some contractors believe installing subsurface dripline under a grassBut what about under existing sod? Some contractors believe installing subsurface dripline under a grass lawn that’s already established is too difficult; others will say it’s a simple matter of trenching it in. Foster says he knows of contractors who’ve based their entire businesses on installing subsurface drip irrigation.

When he’s asked about how easy or hard this is, Lackner says, “That depends. In theory, you could in stall subsurface drip without having to rip up the turf, but it depends on your soil type.”

“If you have coarse, sandy soil, then we recommend you amend it with a denser one, like a loam, just so the water’s able to spread out a little more evenly under the surface of the turf.”

In that type of situation, it might not be as feasible for a retrofit, because you’d need to be adding soil underneath the turf. That’s pretty much impossible to do without ripping the turf out completely.

“But, if you’ve got a denser soil, a dense loam or a clay, I don’t see any reason why it wouldn’t be fairly easy to retrofit it with a trencher,” said Lackner.

In this case, clay soil is a benefit, not a liability. The denser the soil, the more it’s going to distribute water laterally, increasing the capillary action of the soil, as opposed to just draining down vertically due to gravity.

Jeff Davidson is president and owner of Riverview, Florida-based Davidson Landscape and Irrigation; he’s also the president of the Florida Irrigation Society. He’s  retrofitted many of the older homes around Tampa with subsurface drip.

“We’ve installed subsurface in established areas under turf. If the soil’s good, the subsurface drip does its work just fine.”

“However, it’s usually limited to backyards,” Davidson continues. “The reason: somebody’s always coming in to lay new phone or cable lines. If you’ve got drip under the lawn in the front yard, and somebody comes in and puts a new phone or cable line in, and cuts the dripline into pieces, you’ve got a nice big repair job.”

It’s really not that high maintenance

Many contractors believe that drip systems in particular are “high maintenance.” Others disagree.

Primarily, maintenance is a matter of making sure that the filtration system is maintained, according to Foster. Emission holes are tiny. If a filter gets clogged, or the right type isn’t used, or isn’t used at all, the flow of water could definitely be stopped.

“You have to go out and check any irrigation system periodically,” said Gardner. “But some places just don’t have the personnel. They’ll hire a contractor, and he handles five business parks for them, with three or four people going around to all those places.”

Maxvill says that regardless of whether the tubing is on top of soil, placed under mulch or buried deeper, thirsty rodents tend to chew on it. “I’ve seen squirrels dig up dripline, because it’s often not down that deep,” he says. “Those little squirrels will smell the water, bite holes in the plastic, and take out two inches of tubing.”

Troche counters this objection by saying that you need to make sure you’re managing your pests before you install the system.

At least one contractor in Arizona won’t leave his drip tubing above ground. He says it’s the relentless sun, not rodents, that shortens its life dramatically.

“The tubing is supposed to be UV-tolerant,” says Maxvill. “I’m in Texas, and I’ve never had an issue with that. It may get a little hotter in Arizona, but it gets over 100 degrees probably 60 days out of the year here, and can get as high as 113 degrees. I’ve never seen a drip irrigation line have any problem being out in the sun.”

Another thing contractors often mention in the context of subsurface drip is root intrusion. Like an invading army, roots keep marching relentlessly towards water sources. Without some means of stopping them, they’ll eventually penetrate emitters, clogging them.

Dripline manufacturers fight this in various ways. Some use embedded strips of copper inside the emitters, based on the idea that copper ions repel roots. Others use preemergent herbicide embedded in the plastic tubing.