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Fire Pump Room Calculator (NFPA 20)

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Input Data
Enter your project data
Highest flow the pump must deliver (sprinkler demand + hose allowance, or the Fire Protection calculator's pump flow)
Pressure needed at the pump discharge flange at the demand flow (hydraulic calculation result)
Tank at or above the pump: suction flange may drop to −0.2 bar at 150 % flow (§4.16.3.2). City main: ≥ 0 bar (§4.16.3.1)
Tank: lowest water level above the pump (0.1 bar ≈ 1 m). City main: minimum static pressure
Tank: full water level above the pump. City main: maximum static pressure — used for the over-pressure check
Added to the net demand pressure to set the rated pressure. Common practice: at least 7.5–10 %
From the manufacturer's curve if known. NFPA 20 §6.2.2 maximum is 140 %; typical fire pumps 110–125 %
Duty and standby are identical 100 % pumps; they do not run together, so a common suction header is sized for one pump at 150 %
Lowest working-pressure rating among valves, fittings, sprinklers and hose valves in the system
For the power estimate only. End-suction / split-case fire pumps typically 65–80 %
Aboveground sprinkler/standpipe piping only: leave 0. With underground mains, enter the allowable leakage (NFPA 24)
Jockey flow must be less than one sprinkler (K × √0.5 bar) so the main pump starts on any sprinkler operation
0 = use the NFPA 20 Table 4.28(b) minimum. Enter a larger DN to check its velocity at 150 % flow
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Calculation Results
Calculated instantly from your inputs
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Fire Pump Room — NFPA 20

Designs a duty + standby + jockey fire pump room per NFPA 20 (2019).

RATING: flow rounded up to the next standard rating of Table 4.28(b); pumps are rated on NET pressure (discharge − suction).

PERFORMANCE (§6.2): churn ≤ 140 % of rated pressure; at 150 % flow ≥ 65 % of rated pressure.

PUMP ROOM PIPING (Table 4.28(b)): suction, discharge, relief valve and its discharge, flow meter, test header hose valves. Suction sizes are based on ≤ 4.6 m/s at 150 % flow.

OVER-PRESSURE: diesel — if 121 % of churn + max static suction exceeds the component rating, a relief valve is required (§4.20.1.2). Relief valves are only used where NFPA 20 permits them (§4.20.1.1).

JOCKEY (A.4.27.2.1): make up allowable leakage, at least 1 gpm (3.8 L/min), but less than one sprinkler.

SET POINTS (NFPA 20 Annex example): jockey stop = churn + min static; jockey start 0.68 bar lower; main pump start 0.34 bar lower; each additional pump 0.68 bar lower.

DIESEL FUEL TANK (§11.4.1.3.1): 5.07 L per kW + 5 % expansion + 5 % sump.

The pump curve is an ESTIMATE through churn and rated points — always confirm with the manufacturer's certified curve.

Key Points:
  • NFPA 20 standard pump rating (Table 4.28(b))
  • Pump room pipe sizes: suction, discharge, relief, meter, test header
  • Churn ≤ 140 % and 150 % flow / 65 % pressure envelope
  • Relief valve requirement check for diesel pumps
  • Jockey pump sizing (less than one sprinkler)
  • Jockey / main / standby pressure switch settings
  • Driver power and diesel fuel tank volume
Calculation Steps:
  1. Enter all required parameters
  2. Click "Update Calculation"
  3. Review results and analysis