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Go with the Flow

RYAN FRIEDMAN | Drip Irrigation - Low Flow

How many of you out there have held onto a truck until it was well passed its prime? The body was probably peppered with dings and dents, and the odometer had so many zeros on it that you got dizzy every time you glanced down to check the mileage. But you held onto it because you were familiar with every creak and squeak the engine made. Even though you knew it was the smart thing to do, you had trouble moving on.

People fear change, but whether we like it or not, it’s a part of life. The only way to deal with it successfully is to embrace it.

The landscape contracting business has changed. It is not the same as it was 10 years ago. It is not even the same as it was last year. Water, or rather a lack of it in many parts of the country, is largely responsible for this. Nationwide, local and state governments are cracking down on the use of the resource for irrigation. Just recently, municipalities in California, Florida and North Carolina adopted statutes limiting the number of days landscapes can be watered.

In some cities, using water for irrigation has not only been restricted, it has been banned altogether. Many contractors find these developments troublesome. However, they may actually be blessings in disguise. As a result of the nation’s water woes, a number of alternative and sustainable ways to irrigate are growing in popularity. These methods include rainwater harvesting, graywater reuse and low-volume irrigation. Without question, these methods will play a major role in the future of the irrigation industry. By embracing them, contractors will not only expand their customer base and increase their revenue, they’ll be poised to succeed for years to come. Because it is highly cost-effective and extremely efficient, low-volume irrigation, also known as drip irrigation or low-flow, is attracting lots of attention. However, despite this fact, many contractors find it confusing and have been slow to embrace it. But the concept behind low-flow is simple: less is more.

2_2.jpgThese systems deliver small amounts of water slowly and precisely into a plant’s root zone, greatly reducing the likelihood of waste as a result of wind, runoff, or evapotranspiration. “Take any low-flow product that’s out on the market today, and right out of the box it’s going to be 30 percent more efficient than a conventional sprinkler system,” says Travis Komara, president of GPH Irrigation, Rancho Cucamonga, California. One of the reasons that low-flow systems are so efficient is because they completely eliminate the danger of overspray.

“These systems put water only where it is needed. A lot of spray systems end up putting water in areas where it doesn’t belong, like on sidewalks or on the dirt in between plant material,” says Stuart Spaulding, customer and technical service manager at DIG Irrigation Products, Vista, California. “That just doesn’t happen with low-flow systems.”

Overspray is a huge problem. Even when water successfully reaches the plant material it’s meant to irrigate, some of it is often wasted. “The best analogy to think of is getting your kids to drink their milk,” says Susan Thayer, president of Maxijet, Dundee, Florida. “Let’s say you want your kids to drink a gallon of milk in a week. They couldn’t sit down Monday morning and drink the entire gallon at once. You’d have to feed it to them gradually, a glass at a time, throughout all seven days.” The same theory can be applied to plants. If you try to deliver several gallons of water all at once to the plants in your landscape, it’s not uncommon for much of it to run off and be wasted. Most soils just can’t absorb water that quickly. However, if you deliver those gallons slowly, over a period of several hours, the soil has time to absorb the water and make it available to any nearby plants. A lot of the mystery surrounding low-volume irrigation usually disappears once contractors familiarize themselves with the various components that make up a system. Just like conventional systems, all low-flow irrigation systems operate off a main line. 3.jpg

The main line is the pipe that runs from the water source to the valve that controls the rate at which water flows into the system. Many systems also include a sub-main. The sub-main, also known as a lateral, is the pipe located between the control valve and the drip tubing. Submains are usually used only when there are multiple lines of drip tubing feeding off one main line water source. Drip tubing is typically a thin-walled polyethylene tube that is laid on the ground between the plant material . I t can be covered with mulch or left bare. This tubing carries the water from the lateral to the emitters, where it is then distributed to the plant material. Sometimes, not all the plant material you want to irrigate can be reached by the drip line. In these situations, spaghetti tubing is often used to bring water from the drip line to the desired plant material. Spaghetti tubing is a thin—usually less than 10mm in diameter—polyethylene or vinyl tube. It can be placed on the surface and left exposed, or it can be covered with mulch or buried underground.

Let’s say you install a drip line through a long row of shrubs but want to water an oak tree that’s 10 feet beyond those shrubs. Spaghetti tubing would be ideal in this situation. You would simply connect a 10-foot piece of spaghetti tubing to the drip line, attach an emitter to the other end and run it to the base of the tree. All drip systems use some form of emission device.

There are four primary types: inline drip tubing, point source emitters, micro-sprays and bubblers. With inline drip tubing, the emission devices are contained within the tubing itself. The emitters are spaced at regular intervals of 12, 18 or 24 inches, so you can purchase the spacing desired for a particular project. Where you need larger intervals, you can plug those you won’t use, or you can purchase customized tubing and have the emitters placed wherever you want. Emitters are available in a variety of flow rates.

4.jpgEmitters in a given piece of inline tubing always distribute water at the same rate. Because of this fact, and the fact that the emitters are evenly spaced, inline delivers water uniformly and works best where vegetation is densely planted, or wherever plants are located in a line or row (such as a row of shrubs). Point source emitters utilize external emission devices that can be manually placed as needed on the line. Unlike inline tubing, point source emitters don’t have to flow at the same rate. Emitters with different f low rates are matched up to meet the watering needs of the plant material they’re intended to water.

Once you decide where you want to place a point source emitter, you simply punch a hole in the tubing at that location and install an emitter.

Point source is usually used wherever plants are widely or irregularly spaced, because you can place emitters wherever the plants are located.

Both inline and point source emitters come in two varieties: pressure compensating and nonpressure compensating. Pressure compensating emitters deliver a precise amount of water regardless of changes in water pressure. In other words, if water pressure increases, the rate at which the emitter delivers water does not. This ensures that your plant material will never be over-watered or under-watered.

Non-pressure compensating emitters do not adjust to changes in water pressure. Typically these emitters are less expensive but, because they do not compensate for changes in water pressure, you run the risk that your plant material might be over-watered.

Another commonly used emission device is micro-spray. Micro-sprays are very small heads that spray small volumes of water over very short distances. They are sometimes referred to as microjets, mini-sprays, or micro-sprinklers. If you want to cover more of a plant’s root zone, irrigating a slightly wider area, a micro-spray can be ideal. You may only need one or two micro-sprays to adequately water an area, whereas you might need several more point source emitters to cover the same space.

Micro-sprays can also be a better choice than other low-volume methods for beds in which flowers are frequently changed. Many contractors have installed drip irrigation in beds, only to have an unknowing crew come by to change out the flowers and accidentally rip out the drip system as well. Microsprays are more visible, easy to spot and work around.

Finally, bubblers are similar to point source emitters, except that water “bubbles” out of them, typically either running down the sides of the emitters, or spreading out over a few inches in an umbrella pattern. They are typically seen in applications where more water is required (making drip or microspray unsuitable), but is only needed in a small, localized area (where a conventional sprinkler or spray head is unsuitable). They are often used in planter boxes and tree wells. The head assembly, which can also be referred to as a control zone, is another key component of any low-volume system. Typically, it consists of an anti-siphon valve, a filter, a control valve and a pressure regulator. A head assembly can be purchased as a pre-packaged kit or constructed from individually purchased components.

Each piece of the head assembly is necessary to ensure that your system functions safely and properly. Filters ensure that your emitters will remain free from debris. If dirt and other debris is allowed to enter the emitters, they’ll clog and render the entire system ineffective. Anti-siphon valves are also important. These devices prevent water from flowing back into the main line, thereby contaminating your main source of water.

Control valves simply control the rate at which water flows into the system. It is worth noting that many drip irrigation systems contain more than one control valve. For example, one control valve may turn the water on and off to emitters that feed into a collection of shrubs, while another control valve might turn the water on and off to emitters for some hanging pots on the patio of the same property.

The pressure regulator may be the single most important component of the head assembly. Typically, water travels through pipes at a rate of 70 to 90psi. If water is allowed to enter a low-volume system at this speed, it can damage the emitters and other components. “Water traveling that fast can literally blow the emitters off the line,” says Mark Holmquist, business development manager at Efficient Irrigation, NDS, Inc., Lindsay, California. “The ideal rate for low-flow systems is anywhere from 25 to 35psi. Without a pressure regulator, there is no way to keep the water moving at the appropriate rate.”

Although the ideal operating rate is 25 to 35psi, water pressure at the control valve should be slightly higher than that. “You need to account for what is called flow loss,” says Komara. “Every component in the system takes pressure away from the water because of turbulence as it travels through the tubing, hoses and pipes. So if you want water traveling at 35psi as it goes through the drip tubing into the emitters, it should start at the control valve at 45psi.”

Before installing a low-flow system, there are several things you should consider. It’s very important to be aware of the watering requirements of the plant material being used. This information will help you determine exactly how much water will be required and allow you to plan your system accordingly. If you under-build a system, you’re going to end up with dead plants and unhappy customers. On the other hand, if you overbuild a system, you’re wasting money on unnecessary parts and labor.

If there’s ever going to be an ideal time to become familiar with low-flow irrigation, that time is now. “It just makes sense to get involved for so many reasons,” says Komara. “Water shortages, watering restrictions and the green movement make low-volume irrigation an incredibly viable option for both residential and commercial customers.”

 
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