Which of the following statements about pressure is true?

The correct statement is that residual pressure is measured near a flowing hydrant, which is true because residual pressure refers to the pressure in the system when water is flowing, typically assessed at the discharge point, such as a hydrant or the outlet of a hose. This measurement is crucial for understanding how much pressure is available to overcome friction loss and still provide an adequate flow of water to fire suppression efforts.

When a hydrant is flowing, the dynamic nature of the system results in changes in pressure due to factors such as flow rate and the amount of firefighting equipment being used. Measuring the residual pressure in this context helps fire operators to gauge the effectiveness of their water supply and make necessary adjustments based on what they observe.

In contrast, static pressure represents the pressure in the system when there is no flow, such as when the hydrant is closed. Therefore, being able to distinguish between these two types of pressure—static and residual—is vital for effective water supply management during firefighting operations.