Which of the following terms describes the amount of pressure that remains in the water supply system when water is flowing?

The term that describes the amount of pressure that remains in the water supply system when water is flowing is known as residual pressure. This is an important concept in fire protection and hydrant operation, as it indicates the water pressure available for firefighting operations once water is being drawn from the system.

When firefighters connect to a hydrant and start withdrawing water, the static pressure in the system can decrease, and the residual pressure provides insight into how much usable pressure remains under flow conditions. It reflects the effectiveness of the water supply to support firefighting efforts, determining how much water can be delivered at an adequate pressure to reach the fire. This is critical for ensuring that firefighters can effectively combat flames and protect life and property.

The other terms, while related to pressure in a water supply system, refer to different conditions. Flow pressure, for example, focuses on the pressure under flowing conditions rather than the residual amount remaining. Normal operating pressure describes the standard pressure level within a system when no water is being drawn. Static pressure refers to the pressure present in the system when water is not in motion, or no flow is occurring. Understanding these distinctions is key for ensuring efficient firefighting strategies and effective water supply management.