What is considered the Normal Operating Pressure in a water distribution system?

The Normal Operating Pressure in a water distribution system is best defined as the pressure when no hydrants are flowing. This state reflects the baseline or static pressure within the system when the demand for water is minimal, which allows for an accurate measurement of the pressure that should be maintained within the system to ensure adequate service delivery and to avoid issues such as pipe breakage or service interruptions.

When hydrants are flowing, pressures can drop due to the high demand for water, which occurs during firefighting or other large-scale withdrawals, meaning that the system is not under normal operating conditions. Maintenance activities can also temporarily affect system pressure, making those readings unreliable for assessing what should be considered normal. Peak usage hours may temporarily enhance system demand, also leading to variable pressures. Thus, it's the condition without hydrant usage that provides the true representation of the Normal Operating Pressure in the system.