NFPA in USA

NFPA 25 calculator

Hydrant Flow Test Calculator

Calculate hydrant flow from outlet diameter, pitot pressure, and discharge coefficient.

Water Supply AnalysisNFPA 25Workpaper

Calculation workpaper

Enter inputs, review outputs, then use the guidance below before carrying the result forward.

US customary units

Calculation inputs

Enter project screening values in the units shown.

Ready

Worksheet header

Optional project fields for keeping the calculation screen traceable.

Results

Ready

Hydrant flow

1,186.5 GPM

Calculated output

Hydrant flow1,186.5GPM

Before project use

Save the input source, formula, units, warnings, and result with the project record before carrying this screening value into design coordination or AHJ review.

Next calculator: Available Water Supply Calculator

NFPA in USA calculation workpaper

Hydrant Flow Test Calculator

NFPA 25 ยท Water Supply Analysis

nfpainusa.comGenerated record

Project record

Project ID
Not entered
Area
Not entered
System
Not entered
Revision
Not entered
Prepared by
Not entered
Checked by
Not entered

Inputs

Discharge coefficient
0.9
Outlet diameter
2.5 in
Pitot pressure
50 psi

Results

Hydrant flow
1,186.5 GPM

Calculation basis

Formula
Q = 29.83 x Cd x d^2 x sqrt(P)
Reference standard
NFPA 25
Professional boundary
Verify adopted code, project criteria, listed equipment data, and AHJ requirements before relying on this record.
NFPA in USAnfpainusa.comThis is a calculation record, not a signed or sealed engineering document.

Calculation basis

Use the formula and linked reference data after the result is visible. Keep input selection separate from the calculation screen.

Formula

Q = 29.83 x Cd x d^2 x sqrt(P)

Nominal Pipe Diameter

Nominal SizeSchedule 10 ID (in)Schedule 40 ID (in)
3/4"0.8840.824
1"1.0971.049
1-1/4"1.4421.38
1-1/2"1.6821.61
2"2.1572.067
2-1/2"2.6352.469

Professional review path

Use this calculator as a workpaper step: collect evidence, make a review decision, then move the record into the next workflow.

Evidence to collect
  • Outlet diameter measured or recorded for the flowing hydrant outlet.
  • Pitot pressure reading from the same outlet and test condition.
  • Discharge coefficient selected for the outlet condition used in the test.
Review decision
Decide whether the hydrant flow point is reliable enough to feed available-flow analysis or needs field record correction.

Use this result

Use hydrant flow as the measured flow point for water supply review.

Check before use
Confirm outlet diameter, pitot pressure, and discharge coefficient from the same test outlet.
Common pitfall
Incorrect outlet diameter has a squared effect on calculated flow.
Next step
Available Water Supply Calculator

Input evidence

Confirm these values before using the result.

  • Discharge coefficient
  • Outlet diameter (in)
  • Pitot pressure (psi)

Authority basis

Check jurisdiction, AHJ, submittal, and edition records before using this result as project evidence.

AHJ Contact ChecklistInspection and Testing Forms WorkflowNFPA 13, 72, and 25 Edition Basis Worksheet

Record retention

Save the PDF after project fields, inputs, and results are set.

PDF includes

  • Project header and calculator inputs
  • Computed result rows and warnings
  • Formula, reference basis, and professional boundary

Check before filing

  • Input traceability
  • Method review
  • Output reasonableness
  • Professional boundary

Open next

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Engineering disclaimer
NFPA in USA provides engineering workpapers, calculation checks, and reference tables for project screening and coordination. Final design decisions, code interpretations, submittals, and acceptance records must be completed by qualified professionals and verified against the adopted code, project criteria, listings, and Authority Having Jurisdiction requirements. This site does not issue signed or sealed engineering documents.

Related tools and tables

Available Water Supply CalculatorWater Supply Curve PlotterHydrant Flow and Water Supply WorksheetSprinkler Pipe Internal Diameter Reference

FAQ

What is this Hydrant Flow Test calculator for?+
Use it to compute a defined fire protection value from documented inputs, then retain the inputs, result, formula, and warnings with the project record.
Are the results suitable for permit submission?+
Use the saved record only after it is checked against adopted code, project criteria, equipment listings, and AHJ requirements.