Subsurface Drip Irrigation Guide - Contents

TABLE OF CONTENTS

In 1965, Netafim made history with the unique concept of drip irrigation that not only revolutionized traditional irrigation practices but gave us a way to beautify the environment without wasting precious resources. Today, together with 40 years of experience and ambitious, dedicated Research and Development, Netafim continues to take irrigation technology and performance, along with conservation to new heights.

Among its accomplishments, Netafim developed products that have been used successfully in turfgrass since the 1980's. They are a popular choice for a variety of residential and commercial, general and specialized-use turf areas, and have been used very successfully in sports turf as well as composition and grass tennis courts.

There are many myths surrounding the issue of dripperline in subsurface, or below grade applications, especially in turf. That is the reason for this guide. It is time to realize that subsurface irrigation works and works very well. Landscape irrigation contractors are in the business of maximizing the beauty of a property, and drip and dripperline does it better than overhead sprinklers. They do it faster, and they do it while saving water.

As with so many new ideas, we have perfected the fine art of filling in the blanks with negatives. We've all done it. A frequent response is to sidestep potential problems by maintaining the status quo and leaving well enough alone. But there's another twist to it. It's the "If I'm not familiar with it, it must be bad" syndrome. For example, you walk into a store and ask a question about a product or service. Instead of the salesperson admitting that the product isn't sold there, or that they simply don't know the answer, you hear phrases like, "You don't want that," or "That'll never work." Let's be clear, the question was legitimate, it's the answer that wasn't.

Many people imagine that there are no problems with overhead irrigation. To believe that, you must also believe:

• Nozzles are never pointed in the wrong
• Hardscapes, plants and trees aren't direction battered and ruined by spray
• Sprinkler heads don't break
• Spray always reaches into the garden, and the coverage is always perfect.

Here are a few words and phrases that describe the advantages of drip irrigation and dripperline. They appear in no particular order of importance and they help set the stage for what we are going to discuss in this guide:

Netafim is one of the only companies that manufacture a subsurface dripperline product that is proven to work in turf - Techline® CV and Techline® Dripperline. For the purposes of this book we are going to focus on Techline CV, the newer of the two products and the product that incorporates a check valve into every dripper. Note: Techline has proven itself in the most rigorous conditions possible and its dripper, which dates back to 1983, is still performing today around the world. Whenever "Techline CV" is noted, except when we describe a built-in check valve, you can also say "Techline".

We also need to get past a few of the issues that can confuse a legitimate discussion on subsurface irrigation in turfgrass (also known as Subsurface Drip Irrigation or SDI). Once we do that, we can make more sense of the subject.

They include:

The answer rests in how the dripper was designed and what it was intended for.

Most companies that produce dripperline do so with the expectation that the dripperline will end up in a garden environment, laid out in rows, stapled down and covered with a layer of mulch. They never planned on the dripperline being buried in the ground.

There was a time when product designers and sales people fought over whether a dripper should be pressure compensating (PC) or not. From a design standpoint, pressure compensation is more challenging because engineers have to design a dripper that emits the same amount of water over a broad range of pressure. However, the cost to design such a dripper is much more than designing a dripper that simply delivers less and less water along the length of the tubing as the pressure decreases. (Much like a sprinkler or tubing made from ground-up car tires.) Then, in order to bury the tubing, a design solution was needed to keep roots from growing into the emitters and the tubing - which meant designing a dripper that mounts inside the tubing.

There are several products on the market that are either non-pressure compensating or are pressure compensating but cannot protect against root intrusion. But because most rotors and sprays are assumed to be largely the same, companies decided that contractors and end-users probably wouldn't notice that not all dripperlines are created equal.

Conclusion: A non-pressure compensating dripperline is fine for a garden where the run lengths aren't too long and it is being laid on-surface. To install dripperline in a subsurface application, you are going to need a dripperline that has PC drippers and the drippers must be designed with a permanent way to keep the roots from freely invading the dripper outlets.

Techline® CV Dripperline

The Netafim Solution: Techline® CV Dripperline. The drippers in this product were designed for use in rigorous agricultural applications, with the full knowledge that they could end up irrigating a field of crops where the only water source is ditch water, and where, if the system failed, the farmer might lose not only his crop, but his livelihood as well. So when these drippers are used in Techline® CV, you know they were meant for a much harsher world than the drippers designed for a typical homeowner's garden. If Techline® CV will work in agricultural applications, they will certainly work in Mr. and Mrs. Smith's yard.

Note: When other brands of products make their tubing the same color as Netafim, it's a marketing response, not an engineering or product quality response.

Root intrusion can occur by burying a dripperline that was only designed for on-surface application or by not irrigating properly. One is easy to fix, one isn't.

Using an on-surface dripperline in subsurface applications is asking for trouble. Because it isn't always easy to determine what can be used in a specific application, look at the manufacturer's printed product application data. The catalog is always the best place to start. If they do not specifically and clearly say that a product can be used in subsurface applications, or that it can be used in turf, it cannot. If used in a subsurface application, these poorly engineered drippers can and will allow roots to penetrate the dripper opening(s) and grow into the passageways of the drippers, eventually clogging the emitter.

Remember the engineers and sales people battling it out above? Here's what could have happened. They decided to sell their product for garden applications (on-surface or under mulch) because it was easier, it was a good-sized market, and they probably decided not to worry about subsurface, choosing instead to take the Scarlett O'Hara way out. They designed a dripper without concern for roots, and the dripper they came up with is frequently used in on-surface dripperline products. Many companies sell such a product. It has two outlets for each dripper and the tubing has the look of a snake that swallowed a mouse. That is, the tubing's outside diameter (O.D.) increases where the dripper is located. Though brands and models vary, the two holes in a dripper's outlet allow the water to flow out of either or both holes. Importantly, and not for a good reason, the holes are at the immediate end of the dripper's passageway, or labyrinth. Because of this design, the water leaves the labyrinth and the tubing in the same place. This means that the roots have a far easier pathway into the dripper. These drippers are also plagued by the issue of having to capture the water from the inside wall of the tubing, where it is dirtiest. In contrast, water that flows down the center of tubing is the cleanest, but these drippers that bulge on the inside of the tubing cannot get their water from the center of the water flow.

Realizing the inherent flaw in this type of dripper, one company decided to impregnate the dripper with a chemical that would inhibit roots from penetrating the dripper's hole. Actually, this wasn't a bad idea, except that the chemical used is both heat and time sensitive. As long as the chemical remains active and in proper concentrations in the dripper, it will battle the roots. But when the chemical's potency rapidly decreases, the dripper becomes no better than what it was before being chemically altered, and becomes a root sensitive dripper.

We don't want to sour you on the idea of using a chemical to help protect against root intrusion because Netafim sells Techfilter®, a product that uses the same chemical described above but in a renewable cartridge form. Simply put, if chemical protection needs to be replaced, it needs to be placed where people can get to it. In this case, Netafim put it in the rings of a disc filter. When you use Netafim Techfilter and replace the cartridge per instructions, Netafim offers a Limited Lifetime Warranty against root intrusion.

There is another reason why roots could become a problem. The system is being irrigated incorrectly. While it is true that you can promote shallow roots by irrigating daily with overhead sprinklers, you can't compare daily sprinkler watering to daily dripperline watering.

Sprinklers throw water through the air. Depending on the water's velocity and the droplet size leaving the nozzle, the droplets will land somewhere out in the yard. Once there, the droplets sit on the surface, or slowly get absorbed into the soil. As more and more droplets hit the same area, a wetted area on the top of the soil is created. If you water too quickly, exceeding the basic intake rate of the soil much of the water will run off. If you don't lay enough water down, the effect is to create a very shallow area for roots to grow.

In contrast, subsurface dripperline irrigation relies on the soil to hand off and absorb water molecules as you irrigate. Because the dripperline is already below the surface, some of the water moves upward, (through capillary action) some radiates outward and some moves downward. How much is determined by the speed of application and the type of soil.

Note: Always use the lowest flow rate dripper possible. We recommend the following dripper flow rates:

• 0.26 GPH for clay
• 0.4 GPH for loam
• 0.6 GPH for sand

These flow rates not only allow you to maximize zone size, they apply the water at the proper rate for the soil to properly absorb and radiate it.

By irrigating on a daily basis, we develop a very large wetted area below the surface, and as such, two things happen:

Note: The physics and hydraulics are not the same with subsurface dripperline irrigation as they are with overhead sprinklers. As such - those who cleave to the infrequent deep-root watering practice for overhead sprinklers may continue to do so.

The rational is simple. If you allow the soil to go through dry/wet cycles, the area nearest the dripper will be the area where most of the roots will congregate. It will also make it harder for the water molecules to reach outward as far as possible. Note: Daily or every-other-day irrigation allows the area immediately around the dripper to be at or above field capacity. When the soil is in this "super-saturated" state, roots won't grow into that area.

Figure 10 -Transparent view of dripper inside tubing.

Moral: Root intrusion is not a problem if you choose the proper product and irrigate on a daily or every-other-day basis. You are simply maintaining a consistent and balanced level of moisture in the soil allowing the plants and turf to thrive without having to "search" for water. As for the product to use, that is where you need to do your homework. But no method of water application will maintain an optimal mix of air and water in the soil profile better than subsurface drip irrigation.

The Netafim Solution: Use Techline CV Dripperline. Here's why -the dripper uses a single hole outlet, but more importantly, the water leaves the dripper in one place and exits the dripper in another. We call this the "physical root barrier". Water exits Techline CV drippers into an air gap chamber area. When the dripper isn't running, the area is void of water. Also, Techline CV drippers are mounted to the inside wall of the tubing and the inlet area extends down into the center of the tubing where it captures the cleanest possible water. Techline CV Outside Diameter (O.D.) tubing is consistent with no increases in diameter where the dripper is located.