How should a preincident survey gather information about available fire flow in a structure?

Gathering information about available fire flow in a structure is crucial for effective firefighting operations, and flowing a hydrant while taking pressure readings is a direct method to assess the water supply capacity. When firefighters flow a hydrant, they can measure both the static and residual pressures, allowing them to calculate the available flow rate. This process provides essential data regarding how much water can be drawn from the water supply system during an emergency, which is necessary for determining if it will be sufficient to combat a fire in the structure.

In contrast, drawing a floor plan with flow paths mainly helps in understanding the layout of a building and potential fire spread rather than quantifying the water supply. Determining water usage and distribution focuses more on the internal plumbing of the building rather than the external water supply capabilities. Accounting for ventilation sources is crucial for fire dynamics and smoke movement but does not provide information about the water flow available for firefighting efforts. Thus, accurately flowing a hydrant directly addresses the need for understanding the available fire flow.