Variable Output Drip Emitters

Q. I read somewhere not to use the type of drip emitters that you have to open to get water. What say you?

Two emitters are not enough to accurately provide water to a tree as it gets larger. If these emitters flood the area under a tree the water should be captured by a moat or ring of soil surrounding the tree about six feet in diameter. 

A. They are called variable output drip emitters. I don’t like what are called “variable output drip emitters” (the kind that releases a different amount of water depending on how much you “open” it using a dial). You don’t know how much these drip emitters are releasing because there is a loss of precision. Opening it varies the output of water from 0 gph (no water) to 10 gph (wide open). It depends on how much it’s opened, and it doesn’t tell you the amount of water it delivers. “Wide open” might be more than 10 gph for some manufacturers. For me it’s like playing “whack-a-mole” when variable output drip emitters are used. Using variable type drip emitters makes it difficult to tally how much water is used.

Variable flow or variable output drip emitters don't have much precision. You can open it or close it but how much you give a plant is anybody's guess.

The irrigation industry has started to color code drip emitters. If single drip emitter has a specific color, such as red, all of the emitters from that manufacturer are the same. If all the emitters are the color red (2 gph) for example than any drip emitter with a red color will release the water at the rate of 2 gallons per hour. Netafim.