Nozzle Flow vs Pressure and Tip Selection
Flow at the operating pressure from a tip's catalog flow via the square-root law.
Example
You enter
- Tip rated flow (gpm) 0.4
- Rated pressure (psi) 40
- Operating pressure (psi) 60
You get
- Flow at operating pressure 0.490 gpm
Checked against published worked examples from: Spray-nozzle hydraulics / USDA land-grant extension sprayer-calibration guidance.
Details, formula, and sources
ScopeFlow at the operating pressure from a tip's catalog flow via the square-root law, and the pressure that would hit a target flow (flagged outside the flat-fan band). Pressure is a fine-tuning lever -- change tips to change the rate. The EPA label is the law (FIFRA).
Formula or tableNew flow = rated flow x sqrt(operating pressure / rated pressure); required pressure for a target flow = rated pressure x (target flow / rated flow)^2.
Source and editionNozzle-flow square-root relation (standard spray-nozzle hydraulics), by name; USDA / land-grant extension sprayer-calibration guidance.
Free accessThe square-root flow relation is public hydraulics. Extension calibration guidance free on land-grant university extension sites.
What governsEstimate. AHJ and licensed professional govern.
API field namesrated_gpm, rated_psi, new_psi, new_gpm
- Square-root flow law flow scales with the square root of pressure; doubling the flow needs about 4x the pressure and drives the droplets finerspray-nozzle hydraulics
- Flat-fan band a required pressure outside about 15 to 60 psi is flagged -- change to a different tip size insteadextension calibration guidance