Breaking down the basics of drip irrigation

May 10, 2023

I love drip irrigation. I get such satisfaction from seeing the orderly lines of drip tubing in my gardens, emitting precisely measured drops of water onto plant roots.

These commonplace scenes make my small piece of the world feel well-ordered. I know the plants I’m trying to grow are getting water to the root zone, where they most need it. Studies have shown that drip irrigation increases the productivity of vegetables by 18 to 20% or more, versus overhead or furrow irrigation.

I know I’m conserving precious water and only watering plants, not weeds, with drip irrigation. Weeds are minimized in dry climates as the season advances and rains stop. I manage some gardens with overhead irrigation and in those gardens, weeds are relentless, despite regular weeding to remove them before they go to seed. In the drip-irrigated gardens, weeds are minimal once the soil dries in the spring.

There are a number of types of drip irrigation. Many people use ½-inch poly line, with drip emitters popped in at plant locations.

In gardens with a dense planting theme like a flower border, or for hedges, orchard trees or raspberries or strawberries, emitter tubing — ½-inch poly line with emitters built into the line at measured intervals — is an excellent choice.

Emitter spacing options come in 1, 2 or 4 feet. For irrigation efficiency, emitters should be pressure-compensating, usually expressed as "PC" in the product description. Pressure-compensating emitters ensure the emitters at the beginning and end of the line and top or bottom of a slope emit the same amount of water. All vineyards use pressure-compensating emitters. Flange-type emitters are not pressure-compensating.

Many people like ¼-inch flow tubing, often called spaghetti tubing, for containers and small raised vegetable boxes. It is low-profile, extremely flexible and easy to work with. Emitters are built into the line at measured intervals, like 6 or 9 inches. It's not appropriate for larger gardens. The longest runs recommended for each line are 19 feet. The drawbacks of ¼-inch tubing are that the emitters typically clog from minerals (depending on water quality) in one to two years.

One of my favorite, and very underused, drip irrigation products is drip tape.

Drip tape is a high-quality, thin-walled, inexpensive plastic tape that has highly engineered pressure-compensating drip emitters built into the line at measured intervals. It's usually used in large agricultural settings for vegetables but also works great in flower beds and home vegetable gardens. It lasts about seven years, but often much longer.

Its benefits are that it is very inexpensive, long-lasting, easy to use and precise in water delivery. The only detriment is that the tape is easily damaged.

Drip tape is easiest to use in beds that are straight, but the fittings come in the usual couplers, elbows and Ts. With some ingenuity, you can use it in nonlinear settings.

The fittings are ⅝-inch spin loc fittings. They can be used over and over, and if you make a mistake, you can just unlock the fittings, pull them off the tape and use them again.

Holes are easily fixed by cutting out the section of tape with the hole and putting in a coupler fitting. The line is so inexpensive that it's often easier just to replace the line rather than fix the hole. Two thicknesses of tape are available: thin-walled 9 millimeter and thick-walled 15 millimeter.

Specifications:

As each type of drip irrigation system is designed to emit specific amounts of water, don't mix system types.

Dripworks in Willits has a very informative online and print catalog that describes all irrigation system types specifications, in simple and clear language. I use it as a mini textbook and refer to it often.

Kate Frey's column appears every other week in Sonoma Home. Contact Kate at [email protected]. On Instagram @americangardenschool.

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