Sprinkler Precipitation Rate
The precipitation rate a valve zone applies, in 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 and source
precip_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).
First-principles precipitation-rate relation with the Irrigation Association design references and the Rain Bird / Hunter design manuals (by name); no edition cycle.
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