Low Volume, Low Precipitation
“Water, water everywhere,” begins the old poem. Sure, there’s still plenty of water on this planet. However, if the experts are right, we’re going to have a lot less of it in the coming years. Climate change, politics, pollution; all of this affects how much water we’ll either have, or be able to get access to, in the future.
But living things must have water to survive, and turf, plants and trees are no exception. At the same time, a lot of water goes to waste, over-spraying sidewalks and parking lots, and just plain overwatering. It’s increasingly clear that we need to do more with less.
Enter low-volume or micro irrigation. We’re not talking drip irrigation here; that’s in the neighborhood, but it’s not the same house. Low-volume irrigation technology, originally developed for agriculture, has been adapted for commercial and residential applications.
“In general, low-volume irrigation equipment is all about sprinklers and emission devices that deliver low application rates and high uniformity,” said Mike baron, national specifications manager for Toro Water Management. As a result, there’s more water for roses and less to runoff.
You’re going to be hearing a lot about application rates and precipitation rates in this article. Let’s define these terms. “In the past, the terms ‘application rate’ and ‘precipitation rate’ were used interchangeably when referring to the rate at which a sprinkler zone or a particular type of sprinkler head applies water to a given area,” explains baron.
“Now, the Irrigation Association recommends that we use the term ‘precipitation rate’ when water comes from nature’s rainfall, and the term ‘application rate’ when we are referring to a man-made application of water.”
A drought-driven market
Low-volume irrigation is growing in popularity, and drought is the main driver. “Water agencies in the more arid parts of the united States are recognizing that lower application rates mean less runoff,” said baron. Many of those agencies, particularly in the western states, are offering rebates for low-volume installation or retrofits.
Will Pescara is regional landscape director for Memphis, Tennessee-based Mid-America Apartment Communities (MAA). He oversees all the landscape operations, from maintenance to capital improvements, and also manages irrigation for about 31 properties stretching from Jacksonville, Florida to Charleston, South Carolina.
“I started working for their West region, which is primarily Texas,” said Pescara. “Outside of California, Texas is one of the most water-conserving states in the country.” It has to be; in 2012, it was hit with one of the worst droughts this country has even seen, and it’s not over yet.
“We were forced to conserve water, one way or the other,” Pescara explained. “The company had already started looking at water reduction and water conservation, not just from a let’s-reduce-the-bills standpoint, but because it was the ecologically right thing to do. MAA had seen the writing on the wall, with water restrictions coming on the horizon.”
“We were looking at one-day-a-week watering. It was tough. We had a lot of properties with St. Augustine grass, and plants that used a lot of water. When you shut them down to one day a week…well, this was something that really opened our eyes. We thought, ‘If this is happening here, then where else is it going to happen?’” The company considered replacing turf with less thirsty ground covers, using more native plants and exchanging hardscape for landscape. “but we also wanted to keep the attractive appeal of our apartment communities and not have them look real scrubby, where people wouldn’t want to live there.”
“About three-and-a-half years ago, we started testing low-flow nozzles,” continues Pescara. “We outfitted a couple of zones with them, and ran them for five-minute intervals. We saw about a 30 percent reduction in meter readings just from that test. So, we tested out a zone for three to four months, which just happened to be during that period of major drought. Well, the low-flow system never missed a beat, and in fact, did really well in comparison to some of the other zones. The water usage was about 20 to 25 percent less.”
After that successful test, MAA outfitted a lot of turf zones on its properties with low-flow nozzles. “We were able to cut our overall gallons-per-minute usage by 24 percent overall.”
Matched precipitation rate
One of the benefits of low-volume irrigation is that it’s easier to achieve matched precipitation rates, meaning that all the zones in a system are putting out the same amount of water.
“Matched precipitation rates are huge,” said Josh White, president of Conservation Services of America, LLC, Germantown, Tennessee, an irrigation management firm.
“When we know we’re getting the same precipitation rate from different angles of the nozzles, we’re able to take out a lot of the inefficient heads that are putting out different volumes of water at different precipitation rates,” says White. “We won’t have a lot of overwatering. We may run the low-flow heads a little longer than the traditional ones, but we’ll gain in efficiency; a 20 percent reduction in water usage overall. Combined, they’re putting out better distribution with less output over the same time frames. We get universal efficiency, which we don’t get from the conventional nozzles we use.”
Retrofitting old high-volume sprinkler bodies with low-volume sprinkler heads is usually not too difficult. When the major manufacturers started coming out with these products, they had retrofitting in mind. So, micro sprinkler heads by one manufacturer will often fit on bodies made by another. It’s often a simple screw-one-off, screw-another-one-on type of operation.
“Absolutely, it’s an easy retrofit,” says White, “and it doesn’t take a lot of time to unscrew one sprinkler nozzle and screw in another one. The labor in that is very easy—you don’t have to dig anything up, it doesn’t require any shovels whatsoever. It doesn’t take a lot of expertise to do it, and you’re not disturbing anything.”
“In the ideal situation, it can be as easy as that,” says baron. “but what we find many times on retrofits is that heads are crooked, or below-grade, because they’ve sunk into the dirt over time. So then you don’t get the right pop-up height, or they’re not plumb to the ground, or have an old wiper seal that’s leaking excess water, or some other problem.”
“The rotor-type heads don’t retrofit as easily,” White said. “You generally have to replace the entire head. but we look at it this way: it’s still one of the easiest things you can do to upgrade your system. There’s a lot of value in it. The cost differential is not significant, so you get a very quick return on your money.”
Every irrigation contractor knows that water pressures vary a great deal. How does that affect these lower-volume spray heads and rotors? Will the same pressure coming off the main line that worked just fine for the conventional heads cause misting if they’re replaced by low-volume heads?
Pescara was worried about that. “It’s something we did a lot of homework and testing on, before we jumped fullon in,” he said. One thing that helped him was the introduction of pressure-compensating nozzles. These nozzles have discs inside them that can lower the water pressure by as much as 20 percent at the head, without doing anything else.
“At our test site, we had water coming out at 60 to 70 psi,” said Pescara. “The conventional sprinkler heads we tested there misted terribly. When we put the low-volume nozzles on, we did still see some misting, but there was a major reduction. Now that we have the pressure-compensating heads, we’re seeing no misting at all.”
You still might have to make some adjustments to water pressure, however.
“When you lower the application rate, the amount of water flowing through your pipes per minute goes down, and actually helps fix low-pressure problems,” says baron.
“for example, if my system was installed fifteen years ago, and there’s been continued development around me, it may be that the operating water pressure in my sprinkler system has dropped 10 or 15 psi. Now it’s no longer functioning the way it was originally intended, because of that pressure drop.
Low-application-rate nozzles reduce that flow rate by 35 percent and actually solve that low pressure problem very, very nicely.”
“On the other hand, if you have good, decent pressure, lowering the flow rate sometimes results in the pressure going up,” baron adds. “If the pressure goes up too much, you start to lose some of the benefits of the high-efficiency nozzles. You can lose water to misting and overspray.”
Low volume, high ROI The original low-volume heads Pescara tested cost a lot more per unit. “When you start going from a two- to three-dollar nozzle up to a nine-, ten-, 12-dollar nozzle, it’s hard to justify. However, when they introduced low-volume heads with pressure-reducing discs at very little increase in price per head, well, that was a huge plus for us. The conversion is definitely doable within our budgets, and we’re able to show a reasonable return on investment (ROI) to our executive board.”
“The funny thing is, low-flow irrigation heads are a hard sell on the front end,” says Les Nicholas, owner of Rainman Irrigation in Cleveland, Tennessee. “Let’s say a homeowner gets a call from Company X. They say, ‘We’ll put a $2,000 conventional, single-stream, mechanical-rotor sprinkler system in your front yard.’ “Then I come along, and try to explain to this same homeowner that I can put in the identical system for $1,950 dollars, or, I can put in a lowflow rotor system for $2,400. He has a hard time seeing if he should go with the slightly higher-cost system, even though it will save him money in the long run.”
“In fact, I just got through explaining this to a customer. And although he agreed intellectually, he still had a hard time with that $300 to $400 difference. In the end, he went with the cheaper buy.”
You would think that big, commercial clients with a lot of water usage and a lot of irrigation heads would be more eager to snap up these systems. Not if you ask Nicholas.
“That’s a whole other ball of wax. On a lot of these large commercial accounts, I have to deal with a grounds person. He’s never going to pay the water bill, but he’s going to get grief if there’s ever a brown spot in the lawn in front of the main entry. He’s far less concerned about water usage than he is about having that spot be dry.”
“When I’m looking at large commercial projects, if I’m dealing with the person in charge of the account, then I can easily sell a low-volume system. but if I’m dealing with a groundskeeper, he just wants it green at the front entrance, and doesn’t care if he’s got water going down the street. If the grass is green, he’s happy.”
Nicholas does find a market in homeowners who’ve bought houses equipped with “economy” systems that don’t cover terribly well and waste water. “Again, the builder isn’t the one paying the bill. He’s happy to save a hundred bucks on the installation and leave a homeowner with high water bills for the next 10 to 15 years.
So, there’s a great retrofit opportunity.”
“We see much more opportunity as properties are being developed going forward,” says White. “We’re seeing a lot more reduction in landscape and turf, especially in the West, where turfgrass is starting to be seen as a water hog. As restrictions are being put on, I’m seeing a bigger market for any kind of high-efficiency technology.”
Whether low-volume is a hard or an easy sell is a regional thing. Nicholas says that in Tennessee, where water is plentiful, people aren’t worried about it. Low-volume isn’t as big a seller on the Eastern Seaboard for the same reason.
“The East Coast really doesn’t have a lot of water restrictions,” says Pescara. “The mindset isn’t where the people are in the western part of the country, regarding water conservation. It’s just not in the public eye like it is in the West.”
“Water has been so inexpensive in the past that it was easier and less expensive to waste it than to make the changes necessary to use it more efficiently,” says baron. “That’s starting to shift, with the introduction of budget-based tiered rates by water agencies. They’ll charge a very modest price for water use within your budget, but if you go over that, you’ll pay 20 to 50 percent more for each additional unit of water. You could suddenly go from paying $100 a month to paying $2,000 a month. No one thinks they’re wasting water until they get that bill.”
“When users pay that kind of money, they start paying attention,” baron remarked. “So they’ll call the water agency to do an audit and get recommendations. That’s when they find out that instead of paying that really high bill, they can get help and rebates to implement these new low-volume technologies.”
“We have to explain to them that it’s not blasting water like they’re used to seeing. We tell them, ‘Yes, we’re putting out half as much water as we were.
You may have to run the system 30 or 40 percent longer than you did before, but the end result will still give you a 10 to 20 percent reduction in usage over time.’ This can be hard for people to grasp,” concludes baron.
Low-volume irrigation is better for plant material, as water gets down to the root zones. “With low-volume, we’re getting water that will penetrate down into the ground,” says White. “The droplet sizes are smaller.”
“There really isn’t a soil, maybe other than pure sand, that can absorb the conventional 1.6 inches-per-hour rate,” baron said. “The rest runs off.”
The filtration consideration
A low-volume irrigation system has one special need, and that’s a filtration system. “If you’re going to go to low-volume sprinklers, right after the valve, you should have filters that’ll screen out particulates and possible contaminants,” advises baron. “because these sprinklers have much smaller passageways, they are more sensitive to grit contamination than traditional heads. As you reduce those flow passages, they become more sensitive to any type of contaminants in the water.”
Low-volume irrigation’s moment has definitely come. If you’re not already savvy, learn all you can about it now. Low-volume could become a high-volume business for you down the road.