What term describes the pressure that remains in a water system while water is flowing?

The term that describes the pressure remaining in a water system while water is flowing is residual pressure. This pressure is crucial for understanding how effectively a water system can deliver water under operational conditions. When water is flowing through a system, the pressure that is measured reflects the operational capacity available for that flow, taking into account factors such as friction losses and elevation changes.

When water is not flowing, the pressure within the system is referred to as static pressure, which represents the potential pressure available. However, once water starts flowing, the pressure that is still present while the water moves through the system is retained in the form of residual pressure, and it is essential for ensuring adequate water supply to hydrants, sprinklers, or other fixtures that require a certain pressure to function correctly. Understanding this concept helps in the design and management of fire protection systems and ensures that they can meet the demands placed on them during emergencies.