Reference
DU targets by head type
Achievable low-quarter distribution uniformity depends on the hardware: well-maintained rotors and rotary nozzles distribute more evenly than fixed sprays, so their bands sit higher. These are the grading bands the audit tool applies.
Targets vary by program. These bands follow guidance commonly cited in Irrigation Association auditor training; a rebate scheme or ordinance may set different cut points.
Fixed spray
| DU range | Reading |
|---|---|
| 75% and above | Excellent for fixed spray |
| 65% to below 75% | Within the commonly achievable range |
| 55% to below 65% | Fair - worth diagnosing before rescheduling |
| below 55% | Needs attention before a schedule is trusted |
Rotor
| DU range | Reading |
|---|---|
| 80% and above | Excellent for rotors |
| 70% to below 80% | Within the commonly achievable range |
| 55% to below 70% | Fair - worth diagnosing before rescheduling |
| below 55% | Needs attention before a schedule is trusted |
Rotary nozzle
| DU range | Reading |
|---|---|
| 80% and above | Excellent for rotary nozzles |
| 70% to below 80% | Within the commonly achievable range |
| 55% to below 70% | Fair - worth diagnosing before rescheduling |
| below 55% | Needs attention before a schedule is trusted |
Drip and micro zones
Catch cans cannot sample buried or point-source emission, so no catch-can DU band applies to drip. Drip uniformity is evaluated as emission uniformity from measured emitter flows, a different test with its own targets.
Figures on this page are ranges drawn from manufacturer catalogue data and guidance commonly cited in Irrigation Association auditor training material. They are for orientation and sanity-checking a measured result, not a specification for any particular product or site. Confirm hardware figures against the manufacturer datasheet for the installed nozzle at the operating pressure.
Frequently asked questions
What DU should a fixed spray zone achieve?
Guidance commonly cited in Irrigation Association auditor training treats roughly 65 to 75 percent as achievable for well-maintained fixed sprays, with 75 percent and above excellent. Individual programs set their own cut points, so verify any rebate or ordinance target separately.
What DU should rotors and rotary nozzles achieve?
Commonly cited guidance treats roughly 70 to 80 percent as achievable for well-maintained rotors and rotary nozzles, with 80 percent and above excellent. Their distribution is inherently more even than fixed sprays when matched and maintained.
Why is there no catch-can DU target for drip?
Catch cans cannot sample buried or point-source emission. Drip uniformity is evaluated as emission uniformity from measured emitter flows, which is a different test with its own targets.