What is the final discharge pressure (DP) for Engine 3 when both discharges are used?

The final discharge pressure for Engine 3 when both discharges are used is determined by considering the effects of the parallel operation of the hoses. When both discharges are opened, the flow dynamics change, and the pressure drop can occur due to multiple factors such as friction loss in the hoses and any elevation changes.

In this scenario, a final discharge pressure of 391 psi indicates a careful calculation that takes into account the total pressure available from the engine and the potential losses incurred when both discharges are active. This pressure reflects a balance that allows for effective water delivery while maintaining sufficient pressure to reach the required fire flow demands.

Ensuring this correct pressure allows firefighters to efficiently manage hose lines and ensure they have adequate water supply without compromising performance. An understanding of these dynamics is critical in firefighting operations, especially when multiple lines are drawn from a single apparatus.