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 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 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.
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 relevant internet sites.
Figure A: Planning a Micro Irrigation System
Start by making a sketch of your garden so you can map out the tubing route and the watering devices you decide to use.
Where to buy drip irrigation systems
You can find kits and individual components online and at home centers, garden centers and plumbing suppliers. A basic kit that waters up to 20 containers or a 75-sq.-ft. area costs $25 to $50 and comes with everything you need except the timer. Higherquality kits may cost $70 or more.
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 “Step 6: Drippers, Bubblers, Sprinklers and Sprayers” below 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.
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.
The parts of a drip irrigation system
Battery-operated timer. One 9-volt battery will last an entire season. $30 to $50 depending on the model.
Backflow preventer. Prevents dirty garden water from flowing back into your household water lines.
Screen filter. Traps particles that could clog the emitters. May be separate or part of the backflow device.
Pressure regulator. Lowers the incoming water pressure to a level the drip system can tolerate; 25 to 30 psi is standard.
Hose adapter Connects. water source to the main line.
1/2-in. main line. Don’t exceed 200 ft. of tubing in a single circuit.
Elbow fitting. Connects sections of hose to one another or other components.
Preinstalled emitter. Spaced every 6 to 12 in.; good for straight rows of plants and for shrubs.
Hole punch. Makes ports in the main line to connect watering devices and 1/4-in. tubing.
1/2-gph pressure-compensating dripper. Ideal for flat and hillside terrain and heavy clay soil.
Hose end clamps. Closes off the end of the main line.
1/4-in. barbed tee. Allows branching to 1/4-in. from 1/2-in. lines.
Tubing stakes and adjustable sprayer. You can mix and match watering devices, but don’t use more than 150 gallons per hour (gph) on a single circuit.
1/4-in. micro tubing. Good for containers, zoned areas and customizing your system. Comes in a variety of colors to help hide it. Don’t exceed 50 ft. of 1/4-in. tubing in a single circuit.
1/4-in. barbed connector. Connects 1/4-in. micro tubing to the main line.
Goof plugs. Plug unneeded holes when you change the placement of your tubing, watering devices or landscaping.
Assorted emitters. Adjustable emitters, also called shrubblers and drippers, can apply as little as 1/2 gph or as much as 10 gph. The right number, type and size of emitters depend on plant type, soil and weather conditions. The yellow flag dripper shown can be taken apart and cleaned.
Tee fitting. Creates branch lines to expand and customize the system.
1/2-in. universal coupler. Allows you to cut out damaged tubing and install new line.
Hose end clamps. Closes off the end of the main line.
The basic system
Drip irrigation systems have been around for years, but the early versions were clunky to install and prone to clogging and leaking. Newer systems are affordable, customizable and leak-proof, and they go together easily. System components vary slightly among manufacturers, but generally, you hook up the faucet assembly at the hose bib and run the 1/2-in. main line around your landscape. You can buy main line with prepunched emitter holes or punch your own holes and install in-line emitters. Or you can use leak-proof connectors to run 1/4-in. tubing to where you need it and attach the watering device of your choice. A basic system goes together in just an hour or two and is easy to expand. There are many excellent videos and other resources online to help you plan your system.
These drip systems are pressure compensated, so the water flow is even throughout the length of the tubing. The different emitters and adjustable spray heads let you vary the amount of water based on the weather and plant needs. There are drip watering systems for all sorts of different landscape elements including trees, vegetable gardens, containers and hanging baskets. You can even convert underground sprinklers to drip water systems. The primary differences among them are the kinds of emitters/watering devices they use.
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.
Installation and design tips
- Soak the tubing in warm water or lay it out in the sun for a little while to soften it and make it easier to work with.
- Hold the hole punch at a right angle to the tubing when you punch a hole for an emitter or a connector. This makes a round hole that will seal tightly around the barb of the emitter.
- Flush out the system before installing emitters or other watering devices to clear it of any debris.
- Create your lateral lines (1/4-in. tubing and emitters) before hooking them up to the main line.
- If you have plants with drastically different watering requirements (like trees and containers), you can add or subtract the number of emitters or sprayers for each plant or, even better, break the system up into zones of plants with similar needs.
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.
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).
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.
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.
Also called emitter tubing, drip line consists of 1/2-in. or 1/4-in. tubing with built-in 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.
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.
- 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.
Expert tips for container irrigation
Container gardening expert Rosalind Creasy is a writer, lecturer and landscape designer. She is the author of the 10-book “Edible Gardening” series. She also wrote “Edible Landscaping,” for which she won the American Horticulture Society Book Award.
Creasy says automatic drip irrigation is perfect for containers because they dry out so quickly and require daily watering in hot weather. She’s been using drip irrigation for more than a decade to grow an extensive selection of flowers and edible plants in containers at her northern California home. She says these online retailers—urbanfarmerstore.com, harmonyfarm.com and gardeners.com—are also good sources of information on installation, watering schedules and equipment options.
Here are some of Creasy’s tips for using drip irrigation for containers:
- The goal is for the center of the plant’s root-ball to be damp but not soggy. Set a timer to water containers twice a day for five to ten minutes, depending on the plant and weather conditions.
- You can also stick a soil moisture probe ($25 online and at garden centers) 6 to 8 in. into the container to check for wetness.
- Watch the plant for signs that it needs water.
- Don’t rely on rain for watering because mature plants shed water off the side of the container.
- Choose adjustable emitters and sprayers with flow control so you can adjust the water pattern for individual plants as they grow.
- For hanging baskets, run the 1/4-in. tubing up posts, under eaves or in the joint between two walls.
- Consider adding a fertilizer injector to the faucet assembly so you can feed your plants while you water. These are available online (they start at about $30) and are installed downstream from the backflow preventer.
- Install a good filter and change it every few months or at least once a season, especially if you have alkaline or mineral-rich water.