If the pump is cavitating, what is a likely cause?

• A. Overheating in the pump motor
• B. A blocked discharge check valve
• C. Inadequate water supply to the pump
• D. Loss of prime or air entering the suction line, preventing continuous water flow

Answer: (D)

Cavitation happens when the pressure at the pump inlet falls below the liquid’s vapor pressure, causing vapor bubbles to form and then collapse as they move to higher-pressure areas. The most direct way this occurs is if the suction line loses its prime or air enters the suction, so the pump pulls air along with the water instead of a continuous water column. That air creates local low-pressure pockets that cavitate, leading to the characteristic noise, vibration, and reduced flow.

Other issues like motor overheating don’t create cavitation directly, and a blocked discharge valve changes discharge flow rather than the suction pressure; while an inadequate water supply can contribute, the primary and most likely cause in this context is loss of prime or air entering the suction line, preventing continuous water flow.