NFPA 25
NFPA 25 Flow Test and Water Supply Calculators
Hydrant flow, pitot flow, available water, and demand comparison tools for inspection, testing, maintenance, and preliminary water supply review.
4 calculators1 reference tablesFormula-first workflow
Tools
4
Calculators in workflow
Reference
1
Lookup tables linked
Standard
NFPA 25
Primary NFPA context
Page role
Use this page for a defined task before moving to the next project record.
- Audience
- NFPA 25 users who need a standard-specific route through calculators, references, worksheets, and authority checks.
- Job
- Coordinate NFPA 25 screening work from initial evidence through calculation review and project handoff.
- Evidence
- Hydrant flow test date, location, static pressure, residual pressure, and measured flow; Outlet diameter, pitot pressure, and discharge coefficient assumptions; Required residual pressure used for available flow comparison
- Output
- Reviewed NFPA 25 assumptions, calculation screens, records, and next-step decisions.
- Next
- Start with the route-selection panel, then open the worksheet, calculator, reference table, or authority workflow that matches the task.
Choose the right route
- 1Use worksheets when the task is a complete project workflow with multiple calculators and QA gates.
- 2Use calculators when one numeric screen is needed and the input evidence is already known.
- 3Use reference tables before calculators when a C value, K-factor, pipe size, density, hazard class, or AWG value must be selected.
- 4Use authority workflows before treating any output as project-ready for submittal, inspection, acceptance, or AHJ discussion.
- 5Use the free tools directly; separate downloadable products are optional and are not required for worksheet or calculator access.
Start here
Start with the worksheet, then use calculators, references, and supporting pages where the workflow calls for them.
NFPA 25 workflow status: Complete
NFPA 25 Flow Test and Water Supply Calculators
| Entry area | Targets | Engineering use |
|---|---|---|
| Worksheets | Hydrant Flow and Water Supply Worksheet | Start with complete workpapers before opening isolated tools. |
| Calculators | Hydrant Flow Test Calculator, Pitot Flow Calculator, Available Water Supply Calculator, Water Supply Curve Plotter | Use calculators as worksheet phase tools, not standalone destinations. |
| Reference tables | Sprinkler Pipe Internal Diameter Reference | Use reference data to justify selected input values. |
| Support content | Water Supply Analysis Workflow, How to Read a Fire Hydrant Flow Test, NFPA 25 Flow Test: Calculate Available Water, Water Supply Curve Basics, Pitot Pressure to GPM Conversion, Available Flow at 20 PSI Residual, Hydrant Test Data Quality Checklist, Water Supply Analysis Fire Protection | Use support pages only for explanations that route back into tools. |
Entry sequence
- 1Start with 1 worksheets that match the standard workflow.
- 2Use 4 calculators only after the worksheet phase identifies the needed screen.
- 3Confirm reference basis from 1 featured reference tables.
- 4Use 8 support pages only as explanations that route back to tools.
NFPA 25 workflow
Use the phases, required records, and review gates to move through the standard workflow without treating the page as a loose link directory.
| Phase | Purpose | Required inputs | Review outputs | Acceptance gate |
|---|---|---|---|---|
Field test capture NFPA 25 | Record hydrant test conditions, pitot pressure, outlet diameter, static pressure, and residual pressure. | Static pressure, Residual pressure, Pitot pressure, Outlet diameter | Hydrant flow, Pressure drop, Flow basis | Field readings are complete and internally consistent before supply curve screening. |
Available water NFPA 25 | Estimate available flow at required residual pressure from the flow test relationship. | Measured test flow, Static pressure, Residual pressure, Required residual | Available flow, Supply curve point, Residual pressure check | Available flow is evaluated at the same residual pressure used by the demand comparison. |
Demand comparison NFPA 25 | Compare available water against sprinkler demand, hose allowance, and pump screening needs. | System demand, Required residual, Pump demand, Hose allowance | Available water screen, Demand comparison, Review flags | Water supply screen is ready for NFPA 13 demand review, NFPA 25 reporting, or pump coordination. |
Required records
- 1Hydrant flow test date, location, static pressure, residual pressure, and measured flow
- 2Outlet diameter, pitot pressure, and discharge coefficient assumptions
- 3Required residual pressure used for available flow comparison
- 4Demand or pump screen used for downstream comparison
Review gates
- 1Static pressure is greater than residual pressure for available flow calculations
- 2Required residual pressure is not below the intended design or review basis
- 3Field test assumptions are documented before comparing against sprinkler demand
- 4Water supply findings are reviewed before acceptance or corrective action decisions
Next-step notes
- 1Use available flow outputs as a water supply screen for sprinkler demand and pump coordination.
- 2Keep the original field test record with any calculated supply curve values.
- 3Confirm final acceptance with the AHJ, owner requirements, and qualified engineering review.
Authority basis
Confirm jurisdiction, AHJ direction, and NFPA edition basis before treating workflow output as project-ready.
Worksheets in this standard workflow
Tools in this workflow
| Tool | Workflow role | Input basis | Primary outputs | Open |
|---|---|---|---|---|
Hydrant Flow Test NFPA 25 | Convert hydrant or flow test observations into water supply screening values. | Discharge coefficient, Outlet diameter, Pitot pressure | Hydrant flow | Open |
Pitot Flow NFPA 25 | Convert hydrant or flow test observations into water supply screening values. | Discharge coefficient, Outlet diameter, Pitot pressure | Hydrant flow | Open |
Available Water Supply NFPA 25 | Convert hydrant or flow test observations into water supply screening values. | Measured test flow, Static pressure, Residual pressure | Available flow | Open |
Water Supply Curve Plotter NFPA 25 | Convert hydrant or flow test observations into water supply screening values. | Measured test flow, Static pressure, Residual pressure | Available flow, Static pressure, Residual pressure | Open |
Featured reference tables
FAQ
What data do I need from a hydrant flow test?+
You typically need static pressure, residual pressure, measured flow, outlet diameter, pitot pressure, and the required residual pressure for comparison.
Why does available flow change with residual pressure?+
Water supply curves estimate how much additional flow is available as residual pressure decreases from static pressure.