When the eye of a pump impeller is positioned above the level of the fluid being pumped, this condition is known as what?

The situation where the eye of a pump impeller is positioned above the level of the fluid being pumped is referred to as "suction lift." This term describes the vertical distance between the fluid level and the pump impeller. In this scenario, the pump must create a vacuum to draw fluid up from below the impeller eye, which requires a certain amount of energy or pressure differential. Suction lift is a critical factor in pump design and operation because it determines the pump's ability to effectively move fluid from a lower level to a higher one.

When evaluating the other terms, "overhead lift" is not a standard terminology used in hydraulic or pumping scenarios, which may lead to confusion. "Gravity head" typically refers to the pressure head generated by the weight of the fluid itself, and while it plays a role in pump operation, it does not specifically denote the position of the impeller. "Lift-off" is not a recognized term in the context of pump operation and may mislead in understanding pumping mechanisms. Thus, the proper term relating to the vertical positioning of the impeller to the fluid level is indeed suction lift.