Sprinkler Precipitation Rate
The precipitation rate a valve zone applies.
Example
You enter
- Zone flow, all heads (gpm) 15
- Zone area covered (ft²) 1200
You get
- Precipitation rate 1.20 in/hr
Checked against published worked examples from: Rain Bird.
Details, formula, and sources
Scopein in/hr (PR = 96.3 x zone gpm / zone area), the number that sets the runtime and the reason spray heads and rotors never share a valve. Head flows come from the manufacturer's nozzle chart; this is a design-rate estimate, not a system audit (irrigation-uniformity audits the installed result).
Formula or tableprecip_in_hr = 96.3 x zone_gpm / zone_ft2 (the 96.3 constant = 231 in^3/gal / 144 in^2/ft^2 x 60 min/hr spreads 1 gpm over 1 ft^2).
Source and editionFirst-principles precipitation-rate relation with the Irrigation Association design references and the Rain Bird / Hunter design manuals (by name); no edition cycle.
Free accessThe precipitation-rate relation and the 96.3 constant are public irrigation-design practice. The nozzle chart and the matched-precipitation rule are in the manufacturer's design manuals.
What governsEstimate. AHJ and licensed professional govern.
API field nameszone_gpm, zone_ft2, precip_in_hr
- Precipitation-rate relation PR (in/hr) = 96.3 x zone gpm / zone area (ft^2)Irrigation Association / manufacturer design manuals
- Head flows the per-head flows are the manufacturer's nozzle-chart values at the operating pressureRain Bird / Hunter nozzle charts
- Matched precipitation sprays (~1.5-2 in/hr) and rotors (~0.4-0.8 in/hr) apply water at very different rates and must not share a valveIrrigation Association design references