This engineering manual outlines verified diagnostic workflows, mathematical calculations, and safety clearances for NFPA 13 Sprinkler Hydraulic Sizing, Remote Area Demand & Fire Pump Head Calculation. Adheres to national and international building standards including NFPA 13 / NFPA 20 / NBC Part 4.
Table of Contents
1. Most Remote Hydraulically Demanding Area
Conforming to NFPA 13 Chapter 19, calculation begins by identifying the most remote design area (1500 sq.ft for Light Hazard, 2500 sq.ft for Ordinary Hazard Group 2).
Discharge Formula: Q = K * √P
Where Q = Flow (GPM), K = Discharge coefficient (5.6 for standard 1/2″ orifice, 8.0 for 3/4″ ESFR), and P = Residual pressure (PSI).
2. Hazen-Williams Friction Loss Equation
p_f = ( 4.52 * Q^1.85 ) / ( C^1.85 * d^4.87 )
Where:
- p_f = Frictional pressure drop per linear foot of pipe (psi/ft)
- Q = Flow rate (GPM)
- C = Roughness factor (120 for black steel pipe, 150 for CPVC)
- d = Internal pipe diameter (inches)3. Fire Pump & Jockey Pump Sequencing
- Main Fire Pump: Cut-in at 85% of rated system static pressure. Cut-out via manual latching push-button.
- Jockey Pump: Cut-in at System Pressure – 10 PSI. Cut-out automatically at full System Static Pressure.
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