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How Irrigation Lines Work

Irrigation lines like this one transfer water from its source, in this case a river, to areas where it can be used to water plants.
Irrigation lines like this one transfer water from its source, in this case a river, to areas where it can be used to water plants.
Davis Turner/Getty Images News/Getty Images

Plants grow where they can get enough water -- it's that simple. If a creek runs dry or the climate changes, dependent plant life dies. If a formally dry area begins receiving regular rain or a river alters course, then new plant life will emerge where the water goes. Vegetation follows its necessary resources and thrives or perishes accordingly.

Eventually, humans decided they wanted to grow certain food plants where they wouldn't otherwise thrive. This was a part of the a­gricultural revolution in which our ancestors learned to cultivate crops and amass a surplus. Later on, humans would desire perfectly manicured yards and gardens as well, often in places that might otherwise support only brambles or nothing at all. To pull off these feats, they learned the art of irrigation, by which they artificially brought water to the land. In its simplest form, this entails manually bucketing the water in. On the more complicated end of the spectrum, humans have diverted floodwaters, built intricate pipe systems and constructed artificial waterways to bring their gardens and farms alive.

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­To get water from point A to point B, and to do so without a lot of bucket hauling, damming or canal building, you'll need to channel it through irrigation lines. Just as power lines transfer electrical power, irrigation lines transfer w­ater for gardens, lawns and crops. In some cases, they also serve as the method of distributing the water, as we'll see in the next section. Irrigation lines play a role in virtually every method of automated irrigation, whether you spend $8 on a soaker hose for your lawn or several hundred dollars an acre on professional farm irrigation.

In this article, we'll take a close look at the way irrigation lines allow us to water crops, lawns and gardens, as well as the problems that can occur.

Subsurface irrigation lines will make this lawn sprinkler system possible without cluttering the yard with pipes.
Subsurface irrigation lines will make this lawn sprinkler system possible without cluttering the yard with pipes.
© iStockphoto.com/Pattie Steib

Several methods of irrigation exist, but the varieties of irrigation line involved break down into three categories: surface, subsurface and elevated. Regardless of how much water you're looking to move, how you distribute it or what you're watering on the other end, you can either bury the line under the soil or keep it aboveground. Each method has its own advantage.

On one hand, a subsurface irrigation line doesn't serve as an eyesore or take up surface real estate. However, just because it's out of sight doesn't mean it won't break or require maintenance. With surface irrigation lines, you obviously won't have to grab a shovel to service a break, but the line is right there on the surface and is potentially subject to more damage from mechanical, human and animal blunders. Some irrigation systems employ elevated lines, which also allow sprinklers to cover larger areas. But since these systems require additional supports and higher pressure, they can be the most expensive irrigation choice. Wheel move irrigation systems are a common form of elevated irrigation line, in which the line serves as the axle for a series of large, rolling wheels.

The materials used to make these lines vary, ranging from strong metals to wood and even stone. One popular modern material is polyvinyl chloride or PVC piping, a form of rugged plastic often used in plumbing. Many manufacturers offer grades and sizes of PVC that are especially made for irrigation lines. Polyvinyl chloride isn't impervious to wear and tear, however. PVC pipes deteriorate over time, especially if subjected to high pressures, large volumes or water hammer (the hammering noise you hear when the flow of water is suddenly stopped). Couplings and cement hold together lengths of PVC piping cement.

­Polyethylene tubing, or high density polyethylene (HDPP) pipe, is another popular irrigation line mat­erial. Resembling lengths of black tubing, poly pipe is more flexible than PVC, often making it easier to install. Lengths of poly pipe secure together with clamps and couplings, but they can also be heat fused.

In many cases, a properly functioning irrigation line simply serves as a conduit for the water between the source and the water delivery system, such as a sprinkler. In other cases, water delivery takes place along the length of the irrigation line, either through mounted sprinklers or holes in the tubing itself. The latter method is key to subsurface drip irrigation, in which water seeps out through a length of buried perforated tubing. In this way, the water goes straight to the roots and doesn't have to trickle down through the soil or potentially pool on the surface.

What can go wrong with irrigation lines? Find out on the next page.

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Yard work can be rough on existing irrigation lines.
Yard work can be rough on existing irrigation lines.
Stephen Swintek/The Image Bank/Getty Images

Broken irrigation lines can cause a great deal of trouble. If water flows out through a busted segment of piping, plants in the immediate area can receive too much water while others go thirsty. Just a small leak can decrease water pressure and volume. If the water volume is high enough, a leak can even damage property and cause mudslides. Therefore, it's important to try to prevent irrigation line problems like breaks from happening and know how to repair them if they occur.

One simple factor to keep in mind is compacted soil. If you bury something underground, guess what happens when you drive a dump truck over the site? Vehicle, human and even pet traffic pushes down on the soil, compacting it and potentially crushing irrigation lines, unless the material is strong enough to withstand the pressure. Likewise, the photo illustrates what can happen when you carry out a little yard work and forget about subsurface irrigation lines. If the lines are located aboveground, your chances of damaging them with lawn and farming equipment may be even greater.

­Cold weather can pose another potential irrigation line problem. If water freezes (and therefore expands) inside your irrigation line, it can burst. To prevent this, some users make sure to flush most of the water out of lines during the winter. Also, the more flexible the material, the more it can withstand the expansion and contraction. For this reason, many landscapers prefer to use poly pipe in cooler regions and PVC in warmer climates.

Irrigation lines are like any other plumbing operation in that they can experience internal blockages. The key is to make sure the water flowing through the lines is properly filtered. Gray water irrigation systems are particularly prone to problems as the previously used water may contain bits of f­ood, hair or other debris. If these bits collect and build up inside the irrigation line, they can clog the pipe and block the system.

Animals can also pose a threat to irrigation lines -- and not just your loveably bored pet dogs and goats, either. Coyotes, gophers and various rodents often chew up poly pipe irrigation lines, mistaking them for food. Don't count out plants, either. If you think your subsurface yard irrigation system is set for life, nearby tree roots may give you a rather rude awakening over the years to come.

The task of repairing broken irrigation lines generally involves two steps: isolating the source of the break or breaks and either patching the break or replacing the segment of pipe or tubing. More advanced irrigation systems employ sensors to determine where flow pressure decreases, thus helping to isolate the point of the break. This technology is especially helpful with subsurface systems. When this isn't an option, farmers, landscapers and gardeners can always fall back on visual inspection. If the pipe is aboveground, you should be able to observe the leak while the water's running. If the pipe is underground, a particularly wet patch of soil above the leak often indicates the break. Then it's just a matter of shutting off the water, digging down and patching or replacing the segment of pipe.

Different irrigation line materials call for different forms of patching. A welding torch may work fine on a metal pipe, but you'll want to cement replacement lengths of PVC piping into place at the couplings and use clamps on poly pipes.

Explore the links on the next page to learn even more about irrigation and lawn care.

Related HowStuffWorks Articles

More Great Links

Sources

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