What is the pressure in a system after water has begun flowing called?

The term used to describe the pressure in a system after water has begun flowing is known as residual pressure. This pressure indicates the amount of pressure left in the system when water is actively moving through the pipes or hoses. During firefighting operations, measuring residual pressure helps determine how much usable pressure remains for effective firefighting and can influence the flow rates and reach of water streams.

Static pressure, on the other hand, refers to the pressure in the system when water is not flowing, providing a baseline measurement. Nozzle pressure is specifically related to the pressure at the nozzle when water is being discharged, which can vary based on flow rates and the diameter of the nozzle. Stream pressure typically pertains to the pressure of the water as it exits the nozzle but is not a standard term defined in the NFPA context like residual pressure is.

Thus, understanding residual pressure is crucial for fire brigade members to assess the effectiveness of their water supply during an emergency response.