For gardeners tired of lugging hoses around the yard, a micro drip irrigation system might be the answer.
A micro drip irrigation system waters plants using a network of small tubes and emitters. It attaches to an outdoor faucet, and the network of tubes snakes through planting beds, slowly delivering water directly to the root zone. The pliable black tubes can be hidden by mulch.
Drip irrigation offers advantages to the home gardener. It wastes far less water than overhead sprinklers or soaker hoses.
It’s customizable and costs about a tenth the price of an in-ground irrigation system.
It’s easy to repair.
Micro drip irrigation works for plants in the landscape and containers. Watering the yard becomes as simple as turning on the faucet.
The downside: It won’t work for lawns. Also, lengths of tubing and flow restrictors and emitters can be a little intimidating for someone who doesn’t normally spend time in nursery supply stores. The average gardener can put this system together, but it requires planning, patience and a little math.
Freedom from lugging hoses at a relatively minor cost makes this do-it-yourself project worth the effort, said Jeff Thompson, a Snohomish County master gardener.
He taught several classes on micro drip systems in the home garden. Thompson and his students put in a system in the beds around the extension office at McCollum Park in Everett, an area that’s larger than the average suburban yard. The supplies cost about $200. An in-ground irrigation system for the same area would have cost about $3,500, he estimated.
He offered to share how to plan and install a system as well as how to avoid common pitfalls.
Planning
Sketch your yard to scale. Draw the features such as lawn, pond, paths, trees, ground covers, plant beds, vegetable garden, the house and shed. Mark the location of any steep slopes. Show the location of the water faucets. Label how frequently plants in your garden need to be watered. The vegetable patch, for instance, might need daily watering. The woody shrubs may only need watering once every few weeks. Sketch in where the supply lines will go. The supply lines need to be within 20 feet of plants.
Next, determine how fast water comes out of the outdoor faucets. This is the most important step for success because it allows you to determine how many gallons per hour the system will deliver and how many emitters can be used on one line, Thompson said.
Here’s how to do the test: Turn the faucet on full blast and time in seconds how long it takes to fill a five-gallon container. Calculate the flow by dividing five by the number of seconds. Then multiply by 3,600 to determine gallons per hour. Here’s an example: Let’s say it takes 70 seconds to fill the five-gallon container. Divide 5 by 70 and the result is 0.0714. Take that number and multiply it by 3,600. The answer is 257 gallons per minute. That’s how much water a typical half-inch micro drip irrigation line can carry in an hour.
Don’t assume all faucets have the same flow. The faucet in the back yard may have a different flow than the one in the front yard.
Thompson said it’s a good idea to set up the system for less than the maximum amount. Try to water too many plants and the water flow may be uneven. He recommended limiting each zone to three-quarters the maximum amount. That way, it allows room for error and gardeners can add more emitters onto the system if needed. If the maximum flow is 257 gallons per minute, three-quarters of that amount is about 192 gallons an hour.
How do you figure how much water plants need? Perennials and small shrubs need about one gallon of water each, Thompson said. Large shrubs require two to three gallons. Ground covers need about half a gallon for every square foot.
Your next job is to carve the yard into zones. Only so much water can be delivered at once so if you have a big yard or lots of plants, you may need several zones. A gardener who has a typical amount of water flowing out of their pipes can water nearly 200 perennials and small shrubs in one zone. If you have a typical suburban yard, you probably could get by with one zone for the back yard. Groups of plants with special watering needs, such as containers or a vegetable garden, need their own zones.
Don’t worry if plants within a zone don’t have exactly the same water needs. This system is adaptable, and emitters can be easily added or subtracted anywhere along the line anytime. That gives you flexibility if you, for instance, have a water-sucking hydrangea in the same planting bed as a Mexican orange. You can put four emitters near the hydrangea and one on the Mexican orange, he said.
Now draw the supply lines onto the map. As a general rule, keep the supply lines to 200 feet or less in one zone. The supply lines should be within 20 feet of all plants so they can be reached by the tubing. If all the plants not within 20 feet, you can redraw the zone or put in a branch with a T barb connector.
Shopping
Now it’s time to go shopping. Kits are available, but the problem is you pay for parts you don’t need or find you don’t have enough of the right parts. Don’t be intimidated by the wall of sometimes oddly-labeled parts.
Shopping list
Manifolds: Optional. Expanders allow you to attach multiple hoses to a faucet. Brass is best.
Quick connects: Optional. Allows you to switch on and off the flow of water. Essential if you set up multiple lines on a manifold. Brass is best.
Y valve: Optional. A valve which has two hose hookups. It allows a hose and an irrigation device to be hooked to one faucet.
Teflon tape: Thin, white material that is wrapped around male threads. Makes it easier to twist two pieces together and prevents leaks.
Timer: Optional. Allows you to time when and how long water will run. Automated timers require less attention than a manual timer but waste water. Manual timers cost about $15 and automated versions start at about $30.
Backflow prevention device: Inexpensive piece of equipment that keeps dirty water from going back into your drinking water supply. Always use them.
Filter: At least 150 mesh; the higher the number, the finer the screen and the more filtration. If you are using gray, pond or well water, special filtration is required. Buy an extra.
Pressure reducer: You can test the pressure of your faucets with a pressure meter. If it’s over 40 pounds per square inch, you need a pressure reducer. Even if it isn’t, Thompson recommends you get one anyway. If you have less than 15 PSI, the water won’t flow through the system properly. Drip operates optimally at 25 or 30 PSI. Most households have around 65 PSI. Buy an extra.
Swivel connector: the swivel connector connects the head assembly to the half-inch supply line. Look for a ¾-inch hose thread that will go with a half-inch polyethylene black distribution pipe. Buy an extra.
Supply lines: You want half-inch tubing, but you don’t want to grab any half-inch tubing. Manufacturers don’t all make half-inch tubing the same size. If you buy different brands of tubing and connectors, the parts may not fit together. Buy everything the same brand at the same store. He recommended buying the 500-foot roll of supply line.
Delivery lines: These attach to the half-inch supply lines. They’re smaller, 1/4-inch tubes. There are two types: vinyl and polyethylene. They work the same except that the vinyl is more pliable and is a better choice for people with dexterity problems. Buy extra.
In-line Valve: If you want to cut off water flow to one area part of the time, you can use an in-line valve. Buy a few extra.
Barb connectors: There are four different types of connectors for creating connections. You only need the straight and the T barb. Buy several of each.
Emitters: The gizmo that attaches to the hose and controls the flow of water to the plant. Pressure-compensated emitters are the best. They deliver a constant stream of water and they can be used on slopes. They are the least likely of all emitter types to become plugged, although they cost slightly more than other types. Thompson didn’t like in-line emitters because he said they clog easily. Spray misters waste water to evaporation and can be a tripping hazard, he said. Buy extra.
Emitters for containers: Any emitters will work with containers, although the line drippers tend to clog. Since container mix is usually porous, it is best to water both sides of the container. Larger containers may need three or four emitters.
Goof plugs: Oops! You didn’t mean to punch a hole there. Use this barb for plugging holes in tubing or sealing the end of a drip line.
Compression coupling: Used for big repairs or to add length to end of supply lines.
Figure-eight end closer: This device allows you to tie off a line temporarily.
Hole punch: A special tool for punching holes in the tubing. Not the same as a paper hole punch.
Stakes: Holds the tubes in place.
Installing
The most complicated part of this project is the planning and shopping. Once you get the pieces home, it shouldn’t take long. Thompson estimated it takes about two hours to set up a system for 100 plants.
All the parts are hand-threaded or hand-tightened or inserted into each other. No glue is required.
Lay out the half-inch supply lines in the sun to soften. Letting the tubing get warm makes it more pliable and easier to lay flat on the ground. Next, assemble the head section, the part that attaches to the faucet. The pieces screw together in this order: Timer, backflow prevention device, filter, pressure reducer and swivel connector. If you wish, you can also attach a Y valve before the timer, which allows you to use the faucet without unhooking the head assembly. If you want to use a manifold, place it before the swivel connector.
Don’t forget to use the Teflon tape, which helps prevent leaks when screwing together two parts. Hold the male part in your left hand with the treads toward your left hand. Anchor the tape with your left thumb. Start the tape on treads at top and roll over away from you. Circle three times and tear the tape end. This stuff works great on regular garden hoses, too.
Lay the half-inch tubing in the garden. Attach the half-inch tube to the head. It helps to cut the half-inch tube at a slight angle. Wet the end in warm water and then insert into the swivel connector.
It’s easiest if you attach the emitters to the smaller delivery tubes first and then plug them into the supply line. One end of the delivery tube needs a barb. Take a barb, wet the end, and insert it into the ¼-inch delivery line. Attach the emitter to the other end.
Move from the faucet end of the supply line to the end and attach the smaller delivery tubes as you go. Using the hole puncher, punch a hole into the half-inch tubing and insert the barb end of the prepared emitter line. Place the emitter at the root zone of the plant, never on the crown of the plant. For newly transplanted shrubs, place the emitter at the edge of the soil ball. Emitters are easy to move as the plant grows, and more can be added later, if needed.
Want to run a line under a sidewalk? Dig a short trench on either side of the walkway. You’re going to use PVC pipe to tunnel under the walkway. Take a length of PVC pipe and cut one at a 45-degree angle. PVC pipe comes in different types and you want the type marked “schedule 40.” Glue a hose connector on the other end. Attach a hose and turn on the water. Twist the tube and apply pressure. When the tube comes through the other side, thread the half-inch transport line through the pipe. The PVC pipe stays in the ground.
If you make a mistake use a goof plug to fill a small hole or a compression coupling if the entire half-inch line is severed. Once all the emitters are in place, turn on the water and flush the system, making sure the line is clear of debris. Close the end with a figure-eight or end compression piece.
Turn on the water and watch the entire system work. Consider adding mulch over the system so it’s invisible.
Everything except the head parts can be left outside during the winter. But the head parts can’t handle the cold temperatures so bring everything from the faucet to the swivel connector inside before the first freeze. The next spring, hook up the head pieces, flush the system, and irrigate.
Reporter Debra Smith: 425-339-3197 or dsmith@heraldnet.com.
About Jeff Thompson
A retired physician and longtime gardener, Jeff Thompson learned about micro drip irrigation so he could set up a system in his own Edmonds garden. He completed a professional irrigation course at a local college and now gives two-hour how-to demonstrations on micro drip systems to benefit the Master Gardeners’ Foundation. Reach him by calling the Master Gardener hotline at 425-357-6010.
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