LANDSCAPERS HAVE BEEN WELL SERVED BY USING DRIP IRRIGATION OVER THE YEARS, AND THE TECHNOLOGY CONTINUES TO BE A SOLID OPTION TODAY.
The March 1979 issue of Popular Mechanics laid out the basics for a do-it-yourself irrigation system with the headline, “How a drip can save you some bucks.” An illustration showed rows of plants irrigated by a rudimentary drip system.
The diagram depicts how an outdoor faucet is connected to “antisyphon (sic) device,” which is connected to a “mainline water hose or half-inch diameter black plastic pipe,” which is connected to a pressure-control valve that leads to a header line with five feeder tubes attached to emitting hoses.
Almost 40 years later, the basic layout of a drip irrigation system has not changed all that much. That’s a sign of an effective design that’s withstood the test of time.
Greg Stuhl, owner of Chip-n-Dale’s Landscaping in Las Vegas, has been installing drip systems since he first opened the doors back in 1994. He still uses the same products now that he did back then.
“A drip system is just a very efficient way to deliver water to plants,” Stuhl says. “By changing the emitter flow and having different valves and different stations, it allows you to really be water-efficient and deliver just the right amount of water to each individual type of species.”
As stewards of the landscape, we love water; it’s a good thing. But too much of that good thing can cause problems. Fungus and disease can take out carefully placed plants, and high alkalinity can cause damage to hardscaping, home siding and patio furniture. These are not things you want to pass on to your customers. Nor can we afford to be inefficient or wasteful in the deployment of one of our most valuable resources. Watering restrictions and local ordinances can help keep that in check, but those restrictions can also put constraints on how landscapes are maintained.
Not a new concept
Drip irrigation solves all of these problems. The concept isn’t new, but it’s as if the people who invented it foresaw the future. It remains one of the most effective ways to maintain an ideal moisture level in the soil while virtually eliminating runoff and overspray. It puts the water right where it’s needed, at a plant’s root zone, preventing fungus from developing and preventing damage to hardscaping. It’s precise, effective and efficient.
Besides satisfying these practical concerns, drip irrigation may also bestow some perks. In some areas, a home or business may be exempt from watering restrictions when using drip or have some enticing incentives available for installing it.
For example, the city of Goleta, California will rebate 50 percent of the cost of drip irrigation equipment, up to $2,000. In the city of San Bernardino, California, customers purchasing and installing drip systems in their landscapes may qualify for a 50 percent rebate, up to $150. Your local water district can tell you if your clients qualify for exemptions, incentives or rebates.
Anatomy of a drip system
A drip system is composed of valves, pressure regulators, filters, a backflow preventer, a header line, lateral lines and emitters. Professional-grade kits designed for contractors are available that include all the needed components. The dripline can be installed a few inches below ground, or above ground, covered by mulch.
There are two types of dripline. One type comes with the emitters already embedded in the line, spaced at regular intervals.
“The emitters are pre-installed inside the tubing,” says Mike Baron, a national specifications manager for The Toro Company, Bloomington, Minnesota. “You get a consistent discharge of water every 12, 18 or 24 inches. They’re purchased in coils and configured in grids.” This type of dripline tubing is very popular, because it’s easy to install.
Point-source dripline uses punch-in emitters that can placed anywhere on the line, so they can be aimed precisely and directly at a particular plant’s root zone. This type of dripline is more customizable than the inline type, but also more labor-intensive since emitters must be inserted manually.
Porous pipe, also known as soaker hose or drip hose, is tubing that has been drilled with very fine holes or made out of a porous material. But these may not be the best option for landscape contractors.
“Most sales are to homeowners that need to isolate areas to keep shrubs, trees and groundcover alive,” says Mike Facon, regional sales manager for Landscape Products Inc., Tolleson, Arizona. “The application is not efficient and is not recommended for urban gardens.”
For all its benefits, drip irrigation systems do have some issues. Filtration and pressure regulation at the water source is an absolute must, or debris and high water pressure will damage the emitters. Most of the problems these systems have revolve around those two things.
Emitter clogging can come from a couple of different sources. One source is the plants themselves, especially if the dripline is buried underground, as with SDI, or subsurface drip systems. Roots may eventually find their way into the emitters.
However, methods to circumvent that problem have been developed. Some emitters are treated with copper oxide particles to inhibit root penetration. “Copper is toxic to plant life when found in excess,” says Baron. “In this case, a very small amount is needed to discourage root penetration.” Another way is to pretreat emitters with an herbicide, which is a method some manufacturers use.
Clogging can be caused by the water itself, or, more precisely, what’s in it. Small orifices and narrow tubing mean there’s less space for the water to pass through. If that water has a high sediment load, filtration becomes absolutely critical.
Even with filtration, some types of irrigation water aren’t very compatible with drip systems. Recycled water — water that’s partially treated but not potable — is one.
“A lot of the things I design recycle water over and over again,” says Paul Giacomantonio, the owner of MicroFarm Living Systems in Half Moon Bay, California, a grower of nutritional algae for the natural-foods market. The systems he designs often draw from fish ponds, or use water containing organic nutrients. This recycled water is high in emitter-clogging sediment, so drip isn’t ideal for his operation.
Drip system filters work well, though, for most low-sediment water sources. They’ll keep the water flowing, providing optimal performance for all the emitters. Different types of filters are all widely available.
A hose-end filter can be used for a specific watering area, without having to filter an entire system. Pressure-regulating filters combine two components into one. You’ll need to determine which type of filter makes sense for the system you’re installing.
Another drawback involves nutrition. “The biggest challenge that we have with low-volume drip irrigation is the lack of nutrients,” says Facon. “Most fertilizer is granular and applied via a spreader — that’s why spray irrigation is preferred by a lot of people.”
This can be solved by attaching a fertigation tank. When installed at or near the point of connection to the water source, it will spoon-feed liquid fertilizer into the line, to be dispersed with the water through the emitters to the plants.
Drip irrigation systems are generally designed to operate in the pressure range of 10 to 30 pounds per square inch, but domestic water is usually delivered to households at pressures above 30 psi. Pressure must be reduced with a regulator, or the emitters may pop off.
A 2011 study from New Mexico State University titled, “Low-Pressure Drip Irrigation
for Small Plots and Urban Landscapes” explained it this way: “The flow rate of individual line-source emitters is usually one gallon per hour or less, but flow rate is often expressed as gph per 100 feet, in which case the flow rate per emitter is determined by dividing the flow rate per 100 feet by the number of emitters per 100 feet.”
Here is an example: 15 gph per 100 feet divided by 30 emitters equals 0.5 gph per emitter.
Plan to use 2-gph emitters in sandy soils, and 1-gph emitters if your soil is mostly loam. Identifying your emitter flow rate is part of a planning process that will help you set up a system that is effective and efficient.
Once you make a plan for your system and get it successfully installed, microclimates can be created, which Stuhl says is one of the perks of drip systems.
“Being in Las Vegas, we create a lot of microclimates,” Stuhl says. “We have rose gardens, cactus gardens, tropical gardens, Mediterranean gardens, and ‘fusion’ gardens, which have agaves, roses, palms and cactus in them. Drip allows us to really use a wide variety of plant material in our designs but still make sure those plants are being maintained the proper way with the proper amounts of water.”
Getting in the zone
Customers may need selling on the need to set up and control separate, multiple drip zones around their homes or businesses, because of the various conditions involved. Stuhl says that can be a struggle.
“Educating my clients about the benefits of having multiple zones is the biggest snag I face,” Stuhl says. “A lot of them want to cut corners and put everything on one zone. But if a yard is getting both northern and southern sun exposures, and there’s also a side yard that gets minimal sunlight, it’s really important to spend that little bit of extra money to have a professionally designed system that understands the different microclimates that exist in a yard that contains both sunny and shady areas.”
Start your planning process with list of plants and where they’re located, and review it with your client so he understands why the different zones are needed. If you’ve also designed his landscape with interesting and colorful plant combinations, now you need to convince him of the need to irrigate them efficiently and effectively to keep having pleasing results.
The drumbeat telling us about the need to conserve water grows louder every day; think of Cape Town. Drip irrigation systems are going to become more and more important in the future. Learning how to successfully install these systems now will keep you and your business marching toward that future, and thriving in it.
Going with the flow
The New Mexico University study, “Low-Pressure Drip Irrigation for Small Plots And Urban Landscapes” gives the following formula for determining pressure.
Flow rate per 100 feet + The number of emitters per 100 feet
The full report can be found at: http://aces.nmsu.edu/pubs/research/agmech_eng/RR773.pdf.
The author is a freelance writer and can be reached at email@example.com.