Reference
Precipitation rate ranges by head type
Precipitation rate is how fast a zone applies water, in inches per hour. A catch-can test measures it directly: average catch depth divided by runtime. These catalogue-derived ranges tell you whether a measured figure is plausible for the installed hardware.
| Head type | Typical range | Notes |
|---|---|---|
| Fixed spray | about 1.0 to 2.5 in/hr | High application rate; most soils need cycle-soak under sprays. |
| Rotor | about 0.2 to 1.0 in/hr | Gear-driven rotors apply slowly; runtimes are correspondingly longer. |
| Rotary nozzle | about 0.4 to 0.8 in/hr | Multi-stream rotating nozzles on spray bodies; slower than fixed sprays. |
| Drip / micro | varies with emitter layout | Expressed per emitter in gph, not as an area rate; catch-can PR does not apply. |
Using the range as a sanity check
A spray zone measuring 0.3 in/hr, or a rotor zone measuring 3 in/hr, is more likely a test problem than a system property: a mis-entered runtime, a wrong throat area on mL readings, a partially closed valve, or mixed head types on one valve. The audit tool runs this comparison automatically when you record the head type and spacing.
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 precipitation rate do fixed spray heads apply?
Manufacturer catalogue figures broadly span about 1.0 to 2.5 inches per hour depending on nozzle, pressure, and spacing. A catch-can measurement far outside that span usually indicates a test error rather than a system property.
Why do rotors need longer runtimes than sprays?
Rotors apply water at roughly a fifth to half the rate of fixed sprays (broadly 0.2 to 1.0 inches per hour in catalogue data), so delivering the same depth takes proportionally more minutes.