Standardize Emitters - Gardeners Tip

Standardizing Your

Irrigation Emitters

Bulletin # TP1050

Horticultural Observations
for Healthier Landscapes

Have you taken a stroll through your landscape to inspect your drip irrigation? You need to check for several things:
- Adequate number of emitters for each plant
- Plugged emitters
- Emitter flow rates - equal throughout the zone
A frequent problem I observe is "mixed" emitters.
Shrubblers or fast flow-rate emitters
on the same zone with drips (slow flow rate).
The result is that some plants are getting too much water while others are getting too little. Either water is being wasted or various plants are in stress or not producing properly. Did you know that many plants will not flower properly if being supplied too much water?

Some Popular Types of Emitters

Mixed Rate Drippers (trouble)

Disadvantage of High Rate Shrubblers

Advantage of Slow Rate drips

Some Popular Types of Emitters

High Rate Shrubbler
0 to 15 gph

High Rate Bubbler
0 to 30 gph

Slow Rate Drip
1 to 4 gph (non-PC)

Slow Rate Drip
0.5 to 4 gph (PC)

¼" Slow Rate Dripperline
0.5 to 0.65 gph (PC)

½" Slow Rate Dripperline
0.9 to 1.0 gph (PC)

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Mixed Rate Drippers - If you have mixed flow rates together on the same zone, it is very difficult to provide uniform moisture throughout the root zone. This type of disorganization is a basic cause of water waste and plant stress!
If you reduce the flow on an adjustable high rate emitter to match a drip it is likely to perform erratically. This is due to operating it at the border of its range.
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Disadvantage of High Rate Shrubblers: After doing 300 on-sight consultations for plant stress; High Flow Rate adjustable shrubblers were being used on nearly 75% of the stressed plants. Why?
The reason invariably was that as one high flow emitter was adjusted (or changed due to clogging) this affected all the surrounding emitters on this same zone. Simply "seeing" that water is coming out does not assure that the right amount is coming out. Plus - wet soil does not equate to well watered soil.

Proper Irrigation is a Science
not guesswork

If you have 5 high flow rate shrubblers set at only 50% flow [7 gph] on the same ¼ inch feeder line, the emitters at the emitters will have less than 30% flow [or 4.2 gph]. So, if they are adjusted further open, the actual increase in water in negligible. You wind up taking water from one plant to give to another. Also, because the water is applied more rapidly, it has less capacity to soak deeply into the soil. Shallow water - shallow roots! The perceived advantage of being able to adjust the flow rate has many negative trade-offs.

Measuring the flow from every emitter in the landscape is an enormously labor intensive job. But, the flow can be easily calculated when flow rates are standardized throughout a particular zone.
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Advantage of Slow Rate drips: These are often pressure compensated. This means as you add a few extra to the line (more or larger plants) the flow rate will remain constant. The water for the new plants will not be at the expense of the established plants. Whereas the limit for high rate shrubblers on one zone is typically 15 to 30 gph (if fully opened).
It is practical to have as many as 200 slow rate drips on the same zone without complications. Slow flow rate drips will allow much deeper penetration of water, giving you plants with deeper roots. Deep root systems mean healthier more drought tolerant plants.

The best watering for shrubs and trees is slow and deep. Expanding the watering zone as the plants mature and routinely inspecting for trouble. Set your clock for an hour or more with slow rate drips, and avoid frequent every day scheduling, even in the heat of summer!

If you do happen to have you trees or shrubs on the same zone as your lawn, then and only then would you need high rate emitters, but in order to accomplish this the design often requires soil remediation.

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