Which pressure measurement provides the best indicator of how much more water is available in the system?

The residual pressure measurement is key in determining how much more water is available in a fire suppression system during active firefighting operations. This pressure reading represents the pressure in the system when water is flowing, allowing firefighters to evaluate the water supply's effectiveness under operational conditions.

When water is drawn from the system, static pressure will drop, but the residual pressure will show how much of that water supply remains available. A higher residual pressure suggests that the system can sustain additional water flow without significant drops in pressure, indicating that there is adequate water supply available for firefighting efforts.

In contrast, while static pressure provides a snapshot of the system at rest (no flow condition), it does not reflect how much water will remain once firefighting operations commence. Flow pressure indicates the pressure when water is actively flowing but does not provide a comprehensive view of the available resources beyond that flow. Normal operating pressure could vary widely based on system demand and conditions, making it less reliable for assessing available water. Thus, prioritizing residual pressure is essential, especially in critical situations where understanding the capacity of the water supply can impact firefighting strategies and outcomes.