The standard size of a fire pump can vary depending on the specific application and the requirements of the fire protection system it serves. Fire pumps come in various sizes and capacities to meet the diverse needs of different buildings and facilities. Some common standard sizes of fire pumps are as follows:

1. Small Fire Pumps: These are typically portable or trailer-mounted pumps used for rural firefighting, small commercial properties, or first responder operations. They may have flow rates ranging from around 60 GPM (227 LPM) to 300 GPM (1,136 LPM) and can be powered by gasoline or diesel engines.

2. Mid-sized Fire Pumps: These pumps are often used in mid-sized commercial and industrial buildings. They can have flow rates ranging from 500 GPM (1,893 LPM) to 1,000 GPM (3,785 LPM) and are commonly electrically driven.

3. Large Fire Pumps: These pumps are used in larger commercial buildings, industrial facilities, and high-rise structures. They have higher flow rates, typically ranging from 1,000 GPM (3,785 LPM) to 5,000 GPM (18,927 LPM) or more. Large fire pumps are usually electrically driven and are an essential part of fire protection systems for large-scale applications.

4. Customized Fire Pumps: In some cases, fire pumps may be custom-designed and built to meet specific requirements of unique buildings or facilities with complex fire protection needs. These customized pumps can vary significantly in size and capacity.

It's important to note that the size of the fire pump should be carefully determined based on factors such as the building's size, occupancy, fire protection system design, and local fire codes and regulations. Properly sizing the fire pump ensures it can deliver the required water flow and pressure to suppress fires effectively in the protected premises. Fire protection engineers or specialists play a crucial role in designing and selecting the appropriate fire pump size for specific applications.