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Switching to drip.

Converting an existing sprinkler system is easier than starting from scratch. It also saves time, money, and water.

BY NOW, JUST ABOUT everyone knows that drip (or low-flow) irrigation is an efficient way to water plants. Because a drip system applies water slowly--in gallons per hour (gph) instead of gallons per minute (gpm) like conventional sprinklers--it eliminates wasteful runoff. By applying water directly to plants' roots, it also avoids overspray, evaporative loss, and uneven coverage that results when growing plants block sprinkler spray patterns.

But if you already have sprinklers, switching to drip can seem an intimidating proposition. However, you can simplify installation and minimize expense by retrofitting your existing sprinkler system. Because the distribution lines from the main water source are already in place, you don't have to start from scratch. And there's little or no digging involved.

Over the past couple of years, irrigation manufacturers have introduced many new products that make installation easy for just about anyone. We show four ways to retrofit sprinklers. Which system you choose depends upon the layout of your garden, how plants are arranged, and the number of sprinklers you plan to change over.

Generally, it's best to change over the entire line on one valve, rather than mix sprinklers and drip along it. Because of different water output from sprinklers and drip fittings, it's difficult to adjust watering times on a mixed system. But, in some cases, you may have no choice.


The four systems shown here all use existing underground polyvinyl chloride (PVC) pipe that distributes water through the line from a valve. If your system has galvanized pipe, it's better to start from scratch since pieces of flaking metal can clog the drip emitters.

The photograph for system 1 shows the variety of multioutlet heads available to screw onto sprinkler risers and distribute water to plants through 1/4-inch or laser-drilled soaker tubing. The other three retrofits use traditional drip components.

System 1 is especially useful with mixed plantings of trees, shrubs, and ground covers that aren't grouped according to water usage, gardens where plants are clustered around risers, and small gardens with just a few sprinklers.

If you have extensive plantings and relatively few sprinklers, this system may not work. Each head has a limited number of outlets (from 4 to 12), and you need enough to water each plant individually. If this poses a problem in only a couple of areas, you can add risers.

The heads--called bubblers because they have a higher flow rate than drip--are designed to screw directly onto risers and work under varying pressure, generally from 10 to 100 psi. They come in flow rates from about 2 to 20 gph, depending on pressure.

All of the heads contain small filters or screens and are flow-regulated, so you don't need to install a separate filter and pressure regulator. However, if you irrigate with well water, it's advisable to install a drip filter at the valve.

System 2 is best used in a simple, linear planting bed, such as parking strip or flower bed, and in beds with widely spaced plants. It makes use of one central sprinkler on the line, with the rest capped off as shown.

A filter and pressure regulator (20 to 30 psi) are installed directly on a riser, and 1/2-inch polyethylene tubing weaves around plants to deliver water; one or more emitters (depending on the size of the plant) are punched into the tubing to supply water to each plant's root zone.

The tubing can run 150 feet in any direction (use T-fittings to go in different directions) and can deliver up to about 240 gph. For beds that are fully planted with ground covers or flowers, it's best to use soaker or emitter line instead of 1/2-inch poly.

System 3 is for larger gardens that require more distribution lines and emitters. It's also useful if sprinklers on one line are separated by paving, or if the line serves a large number of plants. To save money, a filter and a pressure regulator are installed at the valve, rather than on multiple risers. Any number of risers on the line can be retrofitted with polyethylene tubing. The rest are capped off.

System 4 converts pop-up sprinklers to drip; this solution is currently available only for Rain Bird pop-up sprinklers 4 inches tall and up. The system is useful for borders with pop-up heads or gardens where the lawn has been replaced with shrubs and ground covers. It can also work as a mixed system if a lawn has been reduced in size and the area has been replanted with flowers and small- to medium-size shrubs.

To retrofit one or several sprinklers, you replace the pop-up innards with a cap and an insert that includes a filter and pressure regulator. You cap off the other sprinklers. Poly tubing or soaker tubing delivers water to plants.


To make your shopping trip as efficient as possible, plan a system on paper first. It also may help you decide whether you want a system that uses 1/2-inch tubing or the multioutlet heads with 1/4-inch tubing.

Draw your garden bed on graph paper and then mark locations of plants. If you choose the multioutlet heads, how much 1/4-inch tubing will it take to deliver water to each plant? If plants are too widely spaced and some of them are a good distance from the sprinkler, the garden may end up looking like a plate of spaghetti with tubing running long distances in all directions (generally a maintenance nightmare). If this is the case, system 2 or 3 with 1/2-inch tubing may be a better choice.

On the other hand, if the landscape configuration is fairly simple, with plants clustered around sprinklers, it may not be worth the trouble to install drip components. Multioutlet heads might do the trick with less work.


In some gardens, it may not be practical to convert an entire line to a low-flow system. The answer may be a mixed system, even though it makes watering trickier.

For instance, if you have a small garden with only one line that waters both the lawn and a small border, you can retrofit a few sprinklers with multioutlet heads to water the border plants while keeping your lawn sprinklers.

Another situation that may call for mixed watering is a reduction in lawn size. If you're planting shrubs and other plants where the lawn used to be, the sprinklers can be retrofitted to water the plants (a good application for system 4).

With a mixed system, you must plan drip output that will water the plants in the same time it takes to soak the grass--usually 15 to 20 minutes two or three times a week. Because of the frequent watering, most drought-tolerant plants won't be suitable.

To water deep-rooted trees and shrubs, you will need a high flow rate (up to 20 gph), such as with system 1. Since water streams out of the 1/4-inch tubing at higher flow rates, install a high-flow diffuser on the end of each piece of tubing.


For selection and service, the best place to shop is at an irrigation supply store (look under Irrigation or Sprinklers in the yellow pages). If you can't find what you're looking for locally, you can order by mail from The Urban Farmer Store, 2833 Vicente St., San Francisco 94116; (415) 661-2204. Catalog $1.

Installing extra risers

To install more risers on an existing line, you need to cut into the PVC pipe. You can then install the riser with an expandable coupling to bridge the gap. Or you can use standard fittings with the following method.

Start by cutting out a 12-inch section of the PVC sprinkler line. Using pipe glue, install an elbow on each cut end.

Make a U-shaped insert by installing four short pieces of PVC (3 to 4 inches long, depending on fittings and pipe used) on either end of two additional elbows. Add a slip/slip/1/2-inch threaded T between the elbows. Glue the fittings after you've adjusted them so the insert fits into the elbows on the cut pipe ends; you may need to recut one piece of pipe for proper fit. Install a 1/2-inch threaded nipple and elbow to the T; screw on the riser. Glue the whole unit in place; after glue dries, flush line, cap off to test for leaks, then bury.
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Title Annotation:includes related article; garden irrigation
Author:Swezey, Lauren Bonar
Date:Jul 1, 1993
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