The choice of a fire water pump is one of the most important decisions to be made in a facility’s fire protection system. This decision should be handled by qualified fire safety professionals and Local Authority Having Jurisdiction (AHJ).
The primary fire water pump should be large enough to maintain pressure above the design pressure at the point in the system farthest from the hydrant. It is also recommended that a spare fire water pump be located nearby so that it will be available if the main fire water pump becomes unusable for any reason, such as a power outage.
When choosing a fire water pump, it is important to look at the PSI and GPM. PSI refers to the force per square inch that the water is pushed with, while GPM refers to how much water can be delivered in a given amount of time.
A fire water pump manufacturer produces a performance curve that plots flow on the “x” axis against net pressure at various flow conditions, from churn or no flow to 150% of the fire pump’s rated flow. A designer can use this information to determine if a particular model of fire pump will meet the requirements of a specific system.
Electric motor driven fire water pumps are the most common means of driving a fire water system and are outlined in NFPA 20 Chapter 9. They take electrical power from a utility connection, generator or other approved source, which turns an electric motor to spin a shaft that drives an impeller that delivers the water. Other types of drivers include diesel engine systems and steam turbine systems. These are less common than electric motor-driven systems due to the need for a backup generator and fuel tanks.