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Fireground Hydraulics Cheat Sheet

Every fireground hydraulics formula a pump operator needs, on one page. Built on validated IFSTA / NFA math. Print it for the apparatus, or bookmark it and build the mental math through practice.

Pump Discharge Pressure (PDP)

PDP = NP + FL + AL ± EL
  • NP nozzle pressure · FL friction loss · AL appliance loss · EL elevation
  • Elevation: +5 psi per floor up (≈0.434 psi/ft); subtract going down.
  • Appliances: ~0 psi under 350 gpm, +10 psi at/above 350 gpm; standpipe +25 psi.

Nozzle Pressures

Smooth bore handline50 psi
Smooth bore master stream80 psi
Fog / combination100 psi
Low-pressure fog75 psi

Friction Loss

FL = C × (Q/100)² × (L/100)
1¾"C = 15.5
2"C = 8
2½"C = 2
3"C = 0.8
4"C = 0.2
5"C = 0.08
  • Flow is squared — doubling gpm quadruples FL. Length is linear.

Smooth Bore Flow

GPM = 29.7 × d² × √NP
⅞" @ 50161 gpm
1" @ 50210 gpm
1¼" @ 50328 gpm
1⅜" @ 80 (master)502 gpm
1¾" @ 80 (master)814 gpm
2" @ 80 (master)1063 gpm

Nozzle Reaction

Smooth: NR = 1.57 × d² × NP
Fog: NR = 0.0505 × Q × √NP
  • One firefighter guideline: ~60 lbf; two-person crew: ~75 lbf.
  • 1" smooth bore @ 50 psi ≈ 79 lbf.

Required Fire Flow

NFA = (L × W) / 3 × %inv × floors
Iowa = (L × W × H) / 100
  • NFA is a whole-structure offensive estimate; Iowa is a known-compartment volume (~30-sec knockdown).

Water Supply Duration

Minutes = Gallons ÷ GPM
  • 1000 gal @ 150 gpm ≈ 6.7 min.
  • 20 min @ 150 gpm needs 3000 gal — more than most engines carry.

Foam Concentrate

Gal = GPM × min × %
  • Class A: 0.1–1% · Class B: 1% / 3% / 6%.
  • 150 gpm × 10 min × 3% = 45 gal concentrate.

Check any of these instantly with the free PumpForge calculators — PDP, friction loss, smooth bore flow, nozzle reaction, required fire flow, and more. For the full breakdown, see How to Calculate PDP.

Frequently Asked Questions

What is the pump discharge pressure formula? PDP = NP + FL + AL plus or minus EL: nozzle pressure plus friction loss plus appliance loss, plus or minus elevation. Add about 5 psi per floor of elevation gain.

What are the fire hose friction loss coefficients? IFSTA/NFA coefficients for FL = C x (Q/100)^2 x (L/100): 1.75-inch = 15.5, 2-inch = 8, 2.5-inch = 2, 3-inch = 0.8, 4-inch = 0.2, 5-inch = 0.08.

What is the smooth bore nozzle flow formula? GPM = 29.7 x d^2 x sqrt(NP), where d is tip diameter in inches and NP is nozzle pressure (50 psi handline, 80 psi master stream).

What nozzle pressures do fire nozzles use? Smooth bore handline 50 psi, smooth bore master stream 80 psi, fog or combination 100 psi, low-pressure fog 75 psi.

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Memorizing a cheat sheet is a start — but on the fireground you need the answer instantly, for any layout. PumpForge lets operators drill PDP, friction loss, and fire streams across hundreds of scenarios with automatic scoring and after-action review. See the platform →