Drop by Drop

Drip irrigation delivers water exactly where it's needed -- the root zone.

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Filed under: Watering, How To

Drip irrigation systems deliver water directly to a plant's root zone so slowly that almost no water is lost through runoff or evaporation.

There are many ways to water plants: by hand using one of several different sprinkler attachments, with soaker hoses, or — if you have a lot of money — you can install an automatic sprinkler system. The most efficient way, however, is to deliver water where it's needed — directly to a plant's root zone.

Drip irrigation isn't a new concept. In ancient times, farmers placed unglazed, porous clay pots near the base of plants and filled the pots with water, which slowly leaked out.

Whether you buy a simple kit and install it yourself or hire a professional to design and install an elaborate system, you will probably recoup the costs in water savings within a year or two. Studies show that a well-designed drip irrigation system uses 30 to 50 percent less water than more conventional watering methods such as head sprinklers. Once you have a drip irrigation system in place, you can say goodbye to the hassle of hauling hoses and moving sprinklers around and say hello to healthier, more productive plants.

A basic drip irrigation system includes a length of plastic tubing into which emitters have already been installed as well as the necessary male and female couplers. Installation is a breeze.

You can design your own system using dozens of different fittings, emitters and miscellaneous parts: straight fittings allow you to connect additional lengths of tubing; tee fittings allow you to split one line of tubing into two; and elbow fittings allow you to make right-angle bends. You can use a simple emitter, which slowly delivers drop after drop of water; misters, which can be installed on stakes to water larger areas; and miniature versions of full-size sprinklers, which can cover a lot of ground.

Drip systems include three essential features:

a backflow preventer, which prevents contamination of your household drinking water
a pressure regulator, which reduces the pressure of your city water supply to one suited for your drip irrigation system
a filter of some type to trap particles that may be in the water; a filter helps to reduce clogging of the system.

The system that Gardening by the Yard host Paul James installs is a simple one. There are more elaborate systems for those who are interested, which include vacuum relief valves, pressure gauges, fertilizer injectors, timers and moisture sensors.

Steps:

From the drip irrigation kit, install the backflow preventer, which is threaded to fit a standard outside faucet connection; to that attach the filter, the pressure regulator and last of all attach the tubing.
Next, lay the tubing. James puts his tubing on both sides of his raised-bed vegetable garden. Here, he has two rows of young black-eyed peas. He could run his tubing down the center of the bed, but there is no point in putting water where it isn't needed, so he runs it down the base of each row and lays the tubing a couple of inches from the base of the plants.

Use metal stakes to hold the tubing in place. The emitters in this tubing are spaced two feet apart, which is ideal for most flower and vegetable gardens; the coverage is complete, and there aren't any bare spots between the emitters. This is important, because if the water were to confine itself to one small area, then the plant roots would also confine themselves to that small area rather than spread out uniformly.

After laying out the tubing, remove the end cap, turn on the water and flush the lines to remove any dirt that might be in the tubing, then turn the water off and replace the cap.

Inspect the system to make sure the water is barely coming out of the emitter — that's the water flow that you want. A faster flow rate would deliver more water than the surrounding soil could absorb, which would lead to runoff; don't be alarmed if your water is just trickling out.

Put down a thick layer of mulch over the area where you lay the tubing. James uses hay or straw. Don't place the tubing on top of the mulch, because the mulch will absorb too much of the water.

When operating your system, make sure you let the water run long enough so that the ground gets soaked but not saturated. You may have to check the moisture level periodically until you get an understanding of how long the system takes to deliver the right amount of water. You want to deep-soak the soil, and that may mean running your system for an hour or two — depending on your soil type.

Even with the best systems and attachments, you still may wind up with a clog in your tubing or emitter, and that’s why you should periodically flush the system and cleans the filter — especially if you live in an area that contains a lot of minerals in the water supply. You can clean the filter much easier than you can replace the emitters.

Or you can consider soaker hoses. They do much the same thing at a fraction of the cost and require almost nothing in the way of installation and maintenance. For those who think that a drip irrigation system is too expensive and difficult, the system that Paul installed cost only $30, and it was a snap to install.