Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?

Correct Answer: Option C — The pump delivers full capacity when started, but gradually slackens off to an abnormally low flow.

Air leakage into the suction side of a centrifugal pump creates a gas-bound condition. Initially, the pump may move fluid, but as air accumulates in the impeller eye, it disrupts the flow path, causing the pump to lose its prime and resulting in a gradual reduction in discharge flow capacity.