Static Liquid Level is defined as the level of the body of liquid from which the pump takes suction when the pump is not operating; for vertical shaft turbine-type pumps, the distance to the liquid level is measured from the horizontal centerline of the discharge head or tee.

• A. Absolute Liquid Level
• B. Pumping Liquid Level
• C. Total Head
• D. Static Liquid Level

Answer: (D)

The main idea is that static liquid level is the reference point for where the pump draws suction when it is not running. This level establishes the suction head the pump must overcome at rest, which is why it’s defined as the level of the liquid from which suction occurs with the pump idle. For vertical shaft turbine-type pumps, NFPA 20 specifies measuring the distance from the horizontal centerline of the discharge head or tee to that liquid surface, providing a consistent reference independent of how the piping is arranged. This static lift is the basis for calculating suction head and, together with friction and velocity heads in the suction line, helps determine the available net positive suction head. Other terms describe different concepts (for example, the level during operation or the total head needed to push liquid to the discharge), so they don’t fit this precise definition of suction reference when the pump is not operating.