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*BETA Version*
Fire Hydrant Flow Calculator
© 2006, Willis Lamm
  • Use the tab key to navigate.
  • Tab between each box to update the calculation.
  • Be sure to tab past your final entry for a correct calculation.

psi before flowing
Residual: psi while flowing
Pitot: pitot gage reading
Diameter: size of opening tested
This hydrant is flowing: GPM from the test outlet
Projected available hydrant flow: GPM Note 1
2nd Static: secondary psi before flowing
2nd Residual: secondary psi while flowing
The main can be expected to flow about: GPM

  1. Projected available flows calculated at 20 psi residual, or the static pressure for low pressure hydrants having static pressures of less than 40 psi.

  2. This calculator is based on established Hazen-Williams formulas and is provided for convenience and estimation purposes only. The author and express no warranty for its suitability for any particular purpose.

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