Fire Flow Calculator — Required Flow & Hydrant Test

Calculate required fire flow (GPM) for buildings using NFA, Iowa/ISU methods and determine available hydrant flow from field tests. This tool helps firefighters, engineers, and inspectors assess water supply adequacy for fire protection.

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Method Description

The NFA (National Fire Academy) method calculates required fire flow based on the floor area involved in fire. It's a straightforward approach widely used for initial fire flow estimations.

Required GPM = (Length × Width × Floors on Fire) / 3

This method assumes typical fire loading and construction. Adjustments may be needed for unusual occupancies or construction types.

References

  • NFPA 1: Fire Code
  • NFPA 1142: Standard on Water Supplies for Suburban and Rural Fire Fighting
  • ISO Commercial Risk Services
  • MeyerFire Engineering Resources
  • Iowa State University Fire Service Extension

Frequently Asked Questions

What is required fire flow?

Required fire flow is the estimated amount of water needed to control and extinguish a fire in a specific building. It's calculated based on factors like building size, construction, occupancy, and fire involvement.

Which formula should I use?

The NFA method is most commonly used for general calculations. The Iowa/ISU method may be more appropriate for buildings with significant volume. Always check with your local authority having jurisdiction for specific requirements.

How do I perform a hydrant flow test?

Hydrant flow tests involve measuring static pressure (no flow), then opening a hydrant and measuring residual pressure and flow rate. These measurements are used to calculate the available water supply at various pressures.

How accurate are these estimates?

These calculations provide reasonable estimates for planning purposes. Actual fire flow requirements can vary based on many factors including fire behavior, ventilation, and firefighting tactics. Always consult with qualified fire protection engineers for critical applications.

Can I download a printable report?

Yes, use the "Download PDF Report" button to generate a one-page report containing your inputs, selected method, calculated results, and any notes you've added.