In an emergency situation, speed and efficiency of fire suppression can make the difference between life and death for crew members, occupants, or valuable property. A properly sized fire fighting water pump can ensure the system is able to deliver the flow and pressure required to protect those priorities.
The size of the fire pump depends on the elevation of the building or structure, and how far water will have to be piped to get to the site of a fire. Generally speaking, the system is designed to reach the lowest floor of the highest occupiable story with an effective water pressure at that location equal to or greater than the rated gallons per minute (GPM) of the fire fighting pump.
To figure out the GPM, we use a simple equation: GPM = PSI / (Pounds per Square Inch x 60). The PSI is what determines how far the water can travel, and is based on the nozzle and piping size.
Another consideration when sizing a fire pump is friction loss, which can be caused by the length of pipes and the amount of pressure they are under. The best way to calculate this is to use a friction loss calculator.
There are two types of pumps used in firefighting water systems, centrifugal and positive displacement. A centrifugal fire pump is the most popular choice because it is inexpensive, durable and provides high-pressure. However, positive displacement fire pumps are better suited for oil-based fires because they can handle the higher discharge pressures required to release foam to blanket the fire.