Choice Is Wide for Low-Flow Water Systems : Irrigation: Different drip systems serve different plantings. Kits are available for most.
What people call drip irrigation can actually be several types of systems. “Drip” should probably be called “low-flow,” “low-pressure” or “low-volume” irrigation because that’s the one thing the various systems have in common.
The methods all operate on low water pressure with a low rate of application--they deliver the water slowly so it can soak in.
Because they operate at low pressure and low volume, you can hook quite a few devices up to one garden faucet, or one valve. In fact, a big advantage of drip irrigation is that you do not need a lot of valves. One for the front yard and one for the back is usually enough.
Here are the various low-flow systems in broad groups, with some suggestions for starter kits. Pictured are some of the components from the kits, plus a few components available only through irrigation suppliers (see the Yellow Pages), to give you an idea of the great variety available if you are ready to assemble your own system from scratch:
Drip tubing, emitters
This is what most people think of when you say drip--skinny little tubes (one-quarter-inch tubing), often called “spaghetti” with individual “drippers” or emitters, along the way or at the ends. The spaghetti fans out from larger pipes (one-half-inch tubing).
The emitters have very small orifices so that water drips out slowly. As it soaks in it also spreads out so it waters a much larger area than you think.
In the past, these tiny orifices tended to clog, which gave drip systems a bad name, but better filters and “torturous path” or “turbulent flow” emitters have helped tremendously. The filters screen out the inevitable particles found in our water and a zigzag channel inside the emitters keeps the water turbulent so that solids do not have a chance to settle.
Many of the inexpensive starter kits that are commonly available use separate emitters and skinny drip tubing. If you plan to water individual plants--young trees, shrubs or shrubby ground covers--that are spaced several feet apart, this is the easiest system to put together. It is also easy to add onto later.
And if you vary the size of the emitters (which determines how much water comes out, measured in gallons per hour--gph), you can give different plants different amounts of water. It is also easy to figure out how long to leave this kind of system on.
Drip Mist makes inexpensive kits. Raindrip makes several sophisticated starter kits with turbulent flow emitters and pressure compensating devices, as does Drip Irrigation Garden (DIG). Rain Bird makes kits with pressure-compensating emitters with with self-cleaning diaphragms.
Pressure-compensating devices--different than the pressure regulators at the beginning of the system--are contained in each emitter and ensure that the amount of water coming out of emitters at the far end of the system is the same as that close to the faucet.
Such devices are important on long runs of tubing or on hillsides. In fact, it is hard to imagine watering a hillside with anything other than pressure-compensating emitters--there is virtually no runoff and plants at the bottom of the hill get as much as plants at the top.
In-line emitters
In some applications, there are problems with spaghetti tubing and individual emitters. The tubes can be unsightly (you may bury the tubing, but not the emitters), they are in the way when weeding or cultivating, dogs make a mess of them and there are a lot of parts to keep track of.
So when plants are spaced close together (as in flower beds or vegetable gardens or even in areas where trees or shrubs are close together), you might consider “in-line emitters.”
In-line emitters--almost always turbulent-flow types--are hidden inside the main tubing, are between short lengths of solid tubing. Because the tubing is much larger, it tends to stay put, and while you can’t bury the tubing, you can hide it under a mulch.
A particularly nice kit (pictured) is offered through the mail by The Natural Gardening Co. Raindrip also makes a new in-line system.
A variation on this theme uses separate emitters, but they are punched into the sides of larger tubing, with a simple hand punch, so there is not a maze of spaghetti. Again, this works best where plants are fairly close together, although you can vary the placement of the emitters so you are not watering empty ground anywhere. Rain Bird makes a new kit using half-inch tubing. (The pieces, not available as a kit, are available separately through irrigation suppliers. They are made by Olson Irrigation Systems, 10910 Wheatlands Ave., Santee, Calif. 92071, (800) 776-5766.)
Drip tape
Used extensively by agriculture, drip tapes are just beginning to show up as kits. Agricultural tapes are short-lived, designed to be disposable; homeowner versions are sturdier. Some even have tortuous paths molded inside the flattened tube-like tape. They work much like the in-line drip systems, with holes evenly spaced along the lengths of tape.
However, most can not turn corners and must be laid in fairly straight lines or they become pinched, which cuts the flow. Drip Irrigation Garden makes a simple, inexpensive kit with torturous paths molded into the tubing.
Porous piping
Not to be confused with perforated, laser-drilled piping (which is not available in kit form and is intended only for short runs), porous piping “sweats” water though many little pores. It is best when buried. Porous piping is favored in flower beds where plants are very close together because it cannot be seen.
It is possible to run 600 feet of porous piping off a single faucet, and filters are usually not included in kits. Pipes are simply flushed occasionally, but a filter is nevertheless a good idea. Moisture Master makes kits and sells fertilizer injectors/filters separately.
The flow in porous piping is determined by little disks placed at the beginning. Disks that create flows of 1, 2 or 4 gallons a minute are available. Note that this is per minute, not per hour, as flow is usually measured in drip emitters.
(To compare porous pipe to individual emitters, figure out how much water is coming out of any one foot of pipe, by dividing the total flow by the length of the pipe. With the smallest flow disk, a foot of pipe in a run 50 feet long, will have a flow of 1.2 gallon per hour, which is close to the typical 1 gph drip emitter.)
Hydro-Grow is another porous pipe system, available through the mail from Gardener’s Supply.
Mini-sprinklers
The newest idea in low-flow irrigation devices are tiny sprinklers. Unlike regular sprinklers, these put water on slowly, so it has time to sink in and is not lost to runoff. Because the droplets are small, you cannot operate mini-sprinklers when the wind is blowing.
Mini-sprays or jets are similar but simpler still. They are most like the shrub heads used with sprinkler systems--a simple jet of water--but again they apply the water slowly. They cover less area so more are needed but they are almost invisible if the supply pipe is buried.
Neither are for lawns, but are for ground cover areas or other plantings where there are lots of individual plants close together. Gardeners fond of perennials and other flowers like them a lot because they are less trouble-prone and easy to fix.
If they clog, you notice it right away. They are very easy to install--it takes just minutes--and they feel more familiar since you can see how much ground is being wetted.
They are also good for azaleas and other shallow-rooted plants that need a large, shallow area wetted.
Raindrip makes a mini-sprinkler kit and more systems are on the way. Raindrip’s operate at a pressure of 15 pounds per square inch and the 180-degree heads deliver only 6 gallons per hour, compared to an ordinary sprinkler which pours the water at a rate of about 60 to 180 gallons per hour. Putting this kit together is more fun than Tinkertoys.
DIG also makes a kit. (Mini-sprays and sprinklers by Olson Irrigation Systems, not available in kit form.)
No particular drip irrigation system seems to be ideal for all uses. All have their advantages, and gardeners will most likely use more than one kind of drip.
Rows of vegetables will be irrigated one way, flowers another, ground covers another, trees and shrubs yet another. Special plants like azaleas will get their own special system. Conventional sprinklers are still the only way to irrigate lawns.
If this great variety of systems leaves you confused, don’t worry. If you stick with kits, they do come with instructions. Just choose a kit that most suits your needs--for watering flowers, or shrubs, ground covers, or whatever need irrigating more efficiently.
Next: How long you should water.
DRIP-IRRIGATION MANUFACTURERS Drip Irrigation Garden (DIG Corp.), 7916 Ajay Drive, Sun Valley, Calif. 91352. (818) 504-1913.
Drip Mist, P.O. Box A, Carson City, Nev. 89702-1170. Write for installation guide or phone (800) 231-5117 for name of dealer.
Rain Bird National Sales, 145 N. Grand Ave., Glendora, Calif. 91740. Write for installation guide.
Raindrip, 21305 Itasca St., Chatsworth, Calif. 91311. Write for installation guide or phone (800) 367-3747 for name of dealer.
Moisture Master, 225 Larkin Drive, Wheeling, Ill. 60090. Write for installation guide or phone (800) 426 8419 for name of dealer.
MAIL ORDERING DRIP-IRRIGATION SYSTEMS Mail order companies that sell special drip systems:
Gardener’s Supply, 128 Intervale Road, Burlington Vt., 05401.
The Natural Gardening Co., 217 San Anselmo Ave., San Anselmo, Calif., 94960.
In addition:
Harmony Farm Supply, P.O. Box 460, Graton, Calif. 95444, has a wonderful catalogue listing all the various drip system components if you want to design your own. Each kind is compared and the functions of the various parts described. A good source for heavy duty filters.
