What does static pressure refer to in a water system?

Static pressure in a water system is defined as the pressure exerted by the water when it is at rest, meaning there is no movement or flow of water. This measurement is crucial for understanding the potential pressure available in a system, which is particularly important for assessing how well water will flow when valves are opened or fire hydrants are used.

When evaluating the options, the definition of static pressure aligns specifically with a state of rest rather than during any dynamic condition, such as when water is flowing or under high demand. This stability in pressure allows for calculations of system performance and informs system design. Measures related to the water main often include both static and dynamic pressures, but static pressure specifically pertains to the situation when water is not in motion. Therefore, the context provided in the question emphasizes that static pressure is essentially a baseline measurement, allowing for effective water system management and fire protection strategies.