What term refers to the height of a water supply above the discharge orifice?

The term that refers to the height of a water supply above the discharge orifice is 'head pressure.' This concept is essential in fluid dynamics and firefighting, as it describes the potential energy per unit weight of water due to its elevation above a reference point, typically the discharge point. The higher the water source, the greater the head pressure, which affects the pressure available for firefighting operations.

Head pressure is significant for understanding how gravity influences water flow and pressurization in hoses and nozzles. It helps firefighters determine the force available to deliver water effectively during operations, particularly in mountainous or elevated terrains.

The other terms, such as residual pressure and static pressure, refer to different aspects of water pressure systems. Residual pressure relates to the pressure remaining in a water system when water is flowing, while static pressure refers to the pressure in a system when water is not moving. Flow pressure, on the other hand, pertains to the pressure measured under flow conditions but does not specifically address the height of the water supply. Understanding head pressure allows firefighters to make informed decisions about water supply and ensure effective firefighting efforts.