Whether you’re growing roses to win prizes or just trying to keep a few flowerbeds looking good, you know what a chore watering is, lugging hoses around the yard and moving them every half hour or so. Micro irrigation—a network of plastic tubing and low-volume drippers and sprinklers that reach every part of the garden you want to water—takes the hassle out of watering.
The materials are inexpensive (you can get started for less than $100) and easy to install using nothing more than a pruning shears and a special hole punch tool. Once you lay out the tubing and connect the drippers, sprinklers or sprayers, you’ll be able to water your plants by simply turning on the water and letting it run for an hour or two. Add a battery-operated controller for about $40 more and you won’t even have to remember to turn on the water. It’ll turn the water on and off automatically at the times you select.
Micro irrigation saves more than time and energy; it saves water by distributing it more efficiently. Because you use dozens of watering devices to replace one regular sprinkler, you have much greater control over where the water goes and how much is supplied to each plant. Instead of flooding the ground all at once, micro irrigation lets you apply a small amount over longer periods, allowing it to soak into the plants’ root zone for maximum benefit. And since runoff and evaporation are kept to a minimum, micro irrigation uses less water.
Figure A Planning a micro irrigation system
Click Image to enlarge.
In this article, we’ll introduce you to the basics of micro irrigation, including planning tips and step-by-step installation instructions. For more details, especially in the planning phase, we recommend that you also read through one of the manufacturers’ free planning guides or browse the Internet sites we’ve listed (see Buyer’s Guide).
Make a sketch and plan the system
If this is your first venture into micro irrigation, start small and experiment to get a feel for how the system works. Choose one or two flowerbeds or a garden and install a simple one-zone system.
The basic planning strategy is to pick the best watering device to serve each type of plant. Then determine a flow rate that supplies adequate water to every plant in the watering zone. Set up the system to run between one and two hours at a time, two or three times a week.
Start by measuring your garden and making a simple sketch. Choose the type and flow rate of the watering devices based on your soil and the plants’ water needs. Mark these on the plan and draw in the tubing route to connect them. This will involve a little guesswork. See “Drippers, Bubblers, Sprinklers and Sprayers” for information that will help you choose the right watering device. Try to cover all the root zones of your plants. Don’t worry about getting everything perfect at first. Add a few extra of each type of watering device and buy the watering devices, tubing and the basic parts shown in Figure B for the faucet hookup. Once you see how the system works, you’ll find it’s easy to relocate or add emitters to get a more balanced water flow or better coverage.
Figure B Starting from the faucet
A. Battery-operated controller turns the water on and off at specified times. This is optional but should be the first component.
B. Backflow preventer protects your household water from accidental contamination.
C. Filter screens out particles that could clog the holes in the drip parts.
D. Pressure regulator reduces the high house pressure to the lower pressure required by drip systems.
C. Adapter connects the 1/2-in. plastic (polyethylene) tubing to the hose threads on the pressure regulator.
Planning rules of thumb:
•Use 1/2-gph drippers in clay soil, 1-gph drippers in loam and 2-gph drippers in sandy soil.
•Add the gallons per hour (gph) rate of all drippers, bubblers, sprayers and sprinklers you plan to use. If you’re using 1/2-in. tubing for the main line, limit the total to between 150 and 220 gallons per hour (check with the manufacturer).
•Limit the length of 1/2-in. tubing on one zone to a maximum of about 200 ft.
•Limit the total gph on a length of 1/4-in. tubing to 25 to 30.
As you add to the system, it’s best to divide your yard into groups of plants that have similar watering requirements. With this strategy, you add a separate system (zone), starting at the water source, for each group of plants or area of the yard.
For help with planning a large, more complicated system (and for the best prices), work with a retailer that specializes in micro irrigation (see Buyer’s Guide).
Begin at the outside faucet
Figure B and Photo 1 show the parts you’ll need and the order in which to install them. The Y-splitter with shutoffs allows you to keep the drip system on all the time (and operated by a controller) and still use your regular garden hose (Photo 1).You don’t have to use a controller, but you must use a backflow preventer. Some of these components are available with hose thread or pipe thread, so make sure to match the thread type when you buy parts. Joining hose thread to pipe thread will result in leaks.
Lay the 1/2-in. tubing
Next, run the 1/2-in. tubing to the garden bed (Photo 2) and position it according to your plan. The tubing will be more flexible and easier to work with if you let it sit in the sun for a while to warm up. Remember, you can cover the tubing with decorative mulch later to hide it. Cut the tubing with a pruning shears. Use T-fittings to create branches and elbows to make 90-degree bends (Photo 3). Be aware that there are a few different sizes of what’s called “1/2-in.” tubing, depending on which brand you use. Buy fittings to match the brand of tubing you’re using. If you need to join two different brands of tubing or you’re not sure which you have, you can buy universal fittings that will work on all diameters of tubing. Use special plastic tubing clamps to nail the tubing to the house or deck.
You can bury 1/2-in. poly tubing in a shallow trench to conceal it as it crosses a path or small section of lawn, but for longer lengths, especially in high-traffic areas, we recommend substituting 1/2-in. PVC pipe instead. Buy adapters to connect the 1/2-in. poly tubing to the ends of the PVC pipe. Check with your local plumbing inspector before burying any pipe to see whether special backflow prevention is required.
Connect the emitters
Now add the various types of emitters for the particular plants—drippers, sprayers, sprinklers or drip line. The technique is simple. Use a hole punch tool to poke a hole in the tubing wherever you want to add a watering device (Photo 4). You can insert a dripper directly into the hole in the 1/2-in. tubing or use a barbed connector and connect a length of 1/4-in. vinyl tubing. Then connect a watering device to the end of the 1/4-in. tube (Photo 6).
BARBED CONNECTOR
You can buy sprinklers and sprayers as assemblies that include a barbed connector, a short length of 1/4-in. tubing and a plastic stake (Photo 5), or buy the parts separately and assemble them yourself. Remember to buy a selection of 1/4-in. barbed fittings, including T-fittings, elbows, connectors and hole plugs. You can press any of these fittings into a punched hole in the 1/2-in. line and connect 1/4-in. tubes to feed the emitters. T-fittings allow you to run 1/4-in. tubing in opposite directions from the main line or to branch off a 1/4-in. tube. Use connectors to extend a 1/4-in. tube that’s too short. If you punch a hole in the wrong spot or want to remove a fitting, push a hole plug into the hole to seal it.
When your installation is complete, run water through the tubing to flush out any dirt. Then cap the ends (Photo 7). Now you’re ready to turn on the water and see how your new micro irrigation system works. Let the water run for an hour. Then check around your plants to make sure the root zone has been thoroughly wetted. Fine-tune the system by adjusting the length of time you water or by adding or relocating watering devices.
Maintain your system
•Clean the filter once a month (more often if you have well water with a lot of sediment).
•Inspect the drippers occasionally to make sure they’re working.
•In cold climates, prepare for winter by removing the shutoff Y-splitter, backflow preventer, controller, filter and pressure regulator and bringing them inside. Remove end plugs and drain or blow the water out of the system. Replace the caps and plug the faucet end of the tubing as well.
Drippers, bubblers, sprinklers and sprayers
One of the first things you’ll notice when you’re browsing the brochures or Web sites is a wide variety of watering devices. Here are the basic types and a few things you need to know about each one. While the ones shown here are the most common, there are many other, more specialized emitters. See the micro irrigation catalogs for the other types and their uses.
Drippers (20¢ to 70¢ each)
Use these to water individual plants, or buy “inline” drippers and use them in a series with a 1/4-in. tube. Drippers work great for container plants too. They’re color-coded for different flow rates between 1/2 gph (gallons per hour) and 4 gph. In general, use lower flow rates for less porous soil, like clay, to allow more time for the water to soak in. Buy pressure-compensating (PC) drippers to maintain a steady flow despite the water pressure.
Soaker drip line (20¢ to 35¢ per linear foot)
Click Image to enlarge.
Also called emitter tubing, drip line consists of 1/2-in. or 1/4-in. tubing with builtin drippers. It’s available with emitters spaced different distances apart for different flow rates. Drip line is great for vegetable gardens or rows of plants. You can use it to encircle shrubs and large plants, or lay it out in a grid pattern as a substitute for sprinklers in a densely planted flowerbed. Use 1/4-in. drip line for maximum flexibility.
Bubblers (45¢ to 70¢ each)
MIKE KRIVIT
A cross between drippers and sprayers, many bubblers are adjustable for flows up to 35 gph and diameters to 18 in. Since they put out more water than drippers, they’re good for larger plants like roses, tomatoes and shrubs.
Sprinklers (45¢ to $2 each)
These are miniature versions of sprinklers you might use in the yard. Most have flow rates between 14 and 40 gph and cover a radius of 3 to 30 ft. Since most sprinklers have a relatively high flow rate, you can’t use more than about 15 or 20 in one zone of 1/2-in. tubing.
Sprayers (45¢ to $1.70 each)
These are like sprinklers without moving parts. You can choose a spray pattern from a quarter circle up to a full circle, or buy sprayers with adjustable spray patterns. They spray from 4 to 34 gph and up to a radius of about 12 ft. Use sprayers to water ground cover or densely planted flowerbeds.
Buyer’s Guide |
DIG Irrigation Products: (800) 322-9146. www.digcorp.com. Free planning guide available where DIG products are sold. Products available at retail and online stores.
DripWorks: (800) 522-3747. www.dripworks.com. Free design service. Catalog and mail order sales. Excellent Web site and online sales.
The Drip Store: (866) 682-1580. www.dripirrigation.com. Step-by-step online tutorial, forum and shopping for all your micro irrigation needs.
Raindrip: (877) 237-3747. www.raindrip.com. “Micro-Watering Handbook” is free where RAINDRIP products are sold. Free phone advice. Call and ask for Dr. Drip to answer your micro irrigation questions.
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1. Mount a “Y” with shutoff valves to your faucet. Then attach the optional timer, backflow preventer, filter, pressure regulator and adapter.
Click Image to enlarge.
2. Connect the 1/2-in. poly tubing to the faucet end. Then lay the tubing through the garden according to your plan. Stake it down about every 5 or 6 ft.
3. Cut the tubing with a pruning shears and install T- and 90-degree fittings where they’re needed. Twist and press the tubing firmly into the fitting.
4. Punch holes in the tubing wherever you want to install a watering device. Push and twist until the tip of the punch creates a clean hole.
5. Press a barbed connector into the hole in the 1/2-in. tubing. If the 1/4-in. tubing isn’t already attached, add a length of 1/4-in. tubing to reach your dripper, sprayer or sprinkler location.
6. Press pressure-compensating (PC) drippers, sprinklers or sprayers onto the end of the 1/4-in. tubing. Use a stake to support the dripper and anchor it in the root zone of the plant.
7. Flush the system by running water through it. Then use end cap fittings to close the open ends of the 1/2-in. tubing.
