Fire Pump Sizing Calculator
Calculate fire pump GPM, pressure, and motor HP from sprinkler demand per NFPA 20.
Inputs
Results
Total Flow Demand (GPM)
750
Pump Pressure Needed (PSI)
28
Total Required Pressure (PSI)93
Pump Required1
Selected Pump Size (GPM)750
Brake HP Required16.3
Selected Motor (HP)20
How to Use This Calculator
- Enter Sprinkler Demand (GPM), Hose Stream Allowance (GPM), and City Static Pressure (PSI).
- Set Required System Pressure (PSI), Pipe Friction Loss (PSI), and Elevation (feet).
- Review Total Flow Demand (GPM) and Pump Pressure Needed (PSI).
- Use Total Required Pressure (PSI) and Pump Required to inform your decision.
How the result changes with Sprinkler Demand (GPM)
| Sprinkler Demand (GPM) | Total Flow Demand (GPM) | Pump Pressure Needed (PSI) |
|---|---|---|
| 545 | 795 | 28 |
| 1,783 | 2,033 | 28 |
| 3,268 | 3,518 | 28 |
| 4,505 | 4,755 | 28 |
What each input means
- Sprinkler Demand (GPM)
- Required sprinkler system flow rate.
- Hose Stream Allowance (GPM)
- Additional flow for fire department hose connections.
- City Static Pressure (PSI)
- Available static water pressure from city supply.
- Required System Pressure (PSI)
- Pressure needed at the most remote sprinkler head.
- Pipe Friction Loss (PSI)
- Total friction loss through piping system.
- Elevation (feet)
- Height from pump to most remote sprinkler head.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersSprinkler Demand (GPM) = 500, Hose Stream Allowance (GPM) = 250, City Static Pressure (PSI) = 65, Required System Pressure (PSI) = 50 = 6 input(s) provided
- Calculate Total Flow DemandTotal Flow Demand750 = 750
- Calculate Pump Pressure NeededPump Pressure Needed28 = 28
- Calculate Total Required PressureTotal Required Pressure93 = 93
- Calculate Pump RequiredPump Required1 = 1
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