There are many types of commercially available emitters.
A gardener can make her or his own very simple “drip” system by simply putting a hole or holes in a pipe and then running water through it. But as water pressure builds up behind the hole, water will squirt out in a stream – using too much water too quickly and wasting a great deal of it.
Emitters Work Better
Thus emitters were developed. These little devices are placed either directly into main lines or at the end of much smaller tubes attached to the mainline.
The best way to understand how emitters work is to compare them with the end of a hose and what attachments are added to the hose to apply water. There are two basic categories of emitters, and a number of different types.
Pressure Sensitive Emitters
(Also called non-pressure compensating emitters)
These types of emitters deliver a higher flow of water in direct proportion to higher water pressures. This can be compared to a hose with no attachments. Opening the faucet delivers water to the end of the hose. Opening the faucet further increases the speed and pressure of the water at the end of the hose. These are much less expensive than pressure compensating emitters.
Pressure Compensating Emitters
Putting a nozzle or any other delivery head onto the end of the hose regulates the pressure. It really doesn’t matter how much the faucet is opened. The delivery nozzle gives the same flow over a variety of pressure ranges. These may cost several times more than pressure sensitive emitters. They are designed to operate best at about 20 psi, but will work almost as well at 45 psi.
There are a number of different designs of pressure compensating emitters.
Long Path Emitters
In these, water is routed through a long tube, which has a smaller diameter than the main line. The long length of the tube and the smaller size effectively lowers water pressure and water flow. These systems are larger than others because of the length of the tubes required.
Tortuous Path or Turbulent Emitters
These also require long tubes, although not as long as long path emitters. Water runs through these tubes, and hits sharp turns and obstacles inside the tube. These obstacles and turns cause turbulence in the water, reducing the flow and pressure. These emitter systems are cheap and simple. And they work well.
Diaphragm Emitters
These emitters use some type of flexible diaphragm to reduce pressure and flow. Although the diaphragms themselves wear out eventually, they can deliver precise flows to specific areas, and clog much less frequently.
Bubblers
Although not technically drip irrigation, bubblers have many of the same characteristics and benefits that drip systems have.
Bubblers work really well for watering larger plants like roses.
Microsprays
These types of irrigation devices emit droplets or very fine streams of water right above the ground. Similar to sprinklers, but nowhere near as wasteful, they can water circular patterns from between a foot to a dozen feet.
Which Type Is Best for Gardeners?
Unless the garden is very large, complex, has hills or slopes over five feet in elevation difference, pressure sensitive emitters are great. They cost much less than pressure compensating emitters. Pressure compensating systems should be used in sloping or hilly landscapes.
Misters And Foggers
These are not recommended for landscape use.
For more information, see the following articles;
