What is the forward velocity pressure at a discharge opening while water is flowing called?

The term used to describe the forward velocity pressure at a discharge opening while water is flowing is flow pressure. This refers specifically to the pressure that is present at the discharge point as water is exiting the hose or discharge opening, which is an essential factor in fire suppression operations. Understanding flow pressure is critical for determining how effectively water can be delivered to the fire, as it influences the reach and effectiveness of the water stream. It is determined by various factors, including the hydrant pressure, friction losses in the hose, and the elevation of the discharge point relative to the water source.

In contrast, friction loss refers to the pressure lost due to the friction between the water and the walls of the hose or piping, which affects the overall pressure available at the nozzle but does not define the forward motion of the water directly. Head pressure typically pertains to the pressure exerted by a column of water and is not specific to the flow at discharge openings. Residual pressure, on the other hand, is the remaining pressure available after accounting for all losses, which is distinct from the flow pressure measured at the discharge. Understanding these distinctions helps fire service personnel manage and optimize water supply during firefighting operations.