Which of the following is a direct result of impeller wear?

• A. increased efficiency
• B. decreased efficiency
• C. no change
• D. increased head

Answer: (B)

Impeller wear raises hydraulic losses and disrupts smooth energy transfer from the motor to the water. As the blades become thinner, rougher, or spaced differently from the casing, the flow experiences more turbulence and internal leakage, so less of the input energy is converted into useful hydraulic energy. That means the pump becomes less efficient, requiring more power to move the same amount of water. While wear can also cause a drop in head at a given flow, the direct and primary consequence you’ll see is a decrease in efficiency. Increased efficiency or head without a change in other factors doesn’t align with how wear affects the flow paths and energy conversion.