Fire Pump & Tank Sizing Lab
Combine the sprinkler and wet riser demands, pick a listed fire pump size to NFPA 20, set the jockey and pump start pressures, size the motor or diesel engine and the electrical supply, then size the fire water tank. Watch the start sequence play out on a pressure trace.
How to use: start with the defaults or press Import from FF-202 to bring in your sprinkler result. Tap i next to any field for a plain explanation.
1. Demands and supply
The pump must meet the largest of the system demands.
2. Pump room
Duty, standby and jockey pumps with headers, test line and tank. Press play to run the start sequence.
3. Checks
4. Pump curve against demands
Listed pump curve through churn, rated and 150% flow at 65% of rated pressure.
5. Selection summary
6. How the selection works
Which demand governs
The sprinkler demand comes from the hydraulic calculation, plus hose allowance. The wet riser demand to NFPA 14 is 1,893 L/min for the first Class I or III riser and 946 L/min for each extra riser, capped at 3,785 L/min in a sprinklered building, with 6.9 bar at the top outlet. In a combined system the larger demand usually governs.
Choosing the pump
NFPA 20 pumps come in listed ratings. The lab picks the smallest rating that covers the demand flow, then sets the rated pressure from the required pressure minus the suction pressure. A listed pump must give at least 65% of rated pressure at 150% of rated flow and its churn may not exceed 140%.
Pressure settings
The jockey pump stops at churn plus static suction and starts 0.7 bar lower. The duty fire pump starts 0.35 bar below the jockey start, and each further pump 0.7 bar lower again, so the pumps never fight each other.
Driver and power
Shaft power is flow × pressure / (600 × efficiency) in kW with L/min and bar. The motor must not overload anywhere on the curve, so it is checked at 150% flow. Diesel engines lose about 1% for every 5.6 °C above 25 °C, which matters in Gulf pump rooms.
Tank
Effective volume is the total demand × duration. Add the volume below the suction or vortex plate that the pump can never draw. Two compartments let one half be cleaned while the other stays in service.
Learning and checking tool. Final pump selection must use the listed pump curve, the authority's approval and the project fire strategy.