Fire Pump Selection

Fire Pump Selection

Fire pumps should be selected according to their nominal flow and pressure capacities. In our example, the required flow is 295 gpm. Fire pumps must operate at 150% of their rated flow. Therefore, there is no need to select a pump rated for flow demand; this results in an oversized pump. For example, if the flow demand is 295 gpm, a 200 gpm rated fire pump can technically provide that flow.
Many fire pump manufacturers provide selection tools on their websites where the required flow and pressure can be entered, and the results show pumps that can meet these requirements. The NFPA imposes limits on the performance of pumps. This means that the pump curves are not too steep; It allows the pressure increase to decrease rapidly.

As pumps flow at speeds beyond their rated flow, the pressure they can deliver decreases. Some pumps have flat curves where the pressure drops slowly as the flow increases, while others lose pressure more quickly. It is important to consider where the flow requirement lies on the pump curve. At the water flow demand point, the pressure boost provided by the pump must be higher than the required pressure.

Place the required flow and pressure point on the manufacturer’s pump curve for the final check. This point must be below the pump curve for the pump to meet the needs of the suppression system.

There are likely many pumps out there that meet the performance requirements, but having the pressure and flow requirements allows the required flow and pressure point to advance.