How much water does a fire sprinkler head spray per minute?

Civil & DrainageNFPA 13 Sprinkler Standards

Fire Sprinkler K-Factor & Flow Calculator

Calculate water discharge flow in GPM or required operating pressure in PSI for fire sprinkler heads and hydraulic orifices using the standard K-factor formula.

Civil & Drainage Field StandardsNFPA 13 Sprinkler Standards

Engineering formulations calibrated to IPC, UPC & NEC specificationsSub-Zero Cold Climate Tolerances

Quick Summary & Key Answer

Under NFPA 13 fire sprinkler standards, water flow is calculated using the formula Q = K × √P, where Q is flow in GPM, K is the orifice discharge coefficient, and P is residual pressure in PSI. A standard commercial K=5.6 sprinkler head operating at 20 PSI delivers exactly 25.0 GPM.

Standard commercial sprinkler heads have K = 5.6.
NFPA 13 mandates a minimum starting pressure of 7.0 PSI per head.
ESFR (Early Suppression Fast Response) warehouse heads use K-factors of 14.0 to 25.2.

Interactive Calculator

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Solve For

Sprinkler Head K-Factor

Operating Pressure (PSI) or Flow (GPM)

Calculated OutputNFPA 13 Sized

Discharge Water Flow

25.0 GPMGPM

Sprinkler Orifice K-Factor: 5.6
Discharge Formula: Q = K × √P
Minimum Operating Pressure (NFPA 13): 7.0 PSI

Note: NFPA 13 requires a minimum residual starting pressure of 7.0 PSI at the most hydraulically demanding sprinkler head.

NFPA Hydraulic Calculations

K-factor represents the physical geometry and friction coefficient of the nozzle orifice.

Frequently Asked Questions

Common questions regarding this calculation and code compliance

At a typical 20 PSI operating pressure, a standard K-5.6 head discharges approximately 25 gallons per minute (GPM).