In a water flow test using two hydrants, what is the pressure at the hydrant when water is not flowing called?

The pressure at the hydrant when water is not flowing is referred to as static pressure. This term describes the pressure measured in the system when there is no movement of water, which means that there are no additional demands being placed on the water supply.

Static pressure provides a baseline measurement of the water supply's capacity in the system and is important for assessing the fire protection capabilities in case of a fire emergency.

In contrast to static pressure, residual pressure refers to the pressure that remains when water is flowing; this measurement is critical to understanding how much pressure is available to combat fires when hydrants are actively being used. Dynamic pressure is another term associated with flowing water, emphasizing the pressure during water movement. Pump pressure relates specifically to the pressure produced by a pump, and is typically used in scenarios where water is being actively pumped into the system.

Understanding the differences among these terms is key for professionals in fire protection and hydrant operations to properly assess water supply conditions.