The pinging sound from a pump is typically caused by which phenomenon?

• A. Cavitation
• B. Centrifugal action
• C. Water hammer
• D. Vibration

Answer: (A)

Cavitation occurs when local pressure in the liquid drops below its vapor pressure, causing tiny bubbles to form. As these bubbles move to regions of higher pressure or near the impeller, they collapse violently, sending shock waves into the fluid and the pump structure. That rapid bubble collapse creates the sharp, pinging or crackling sounds you hear from the pump. This noise is a classic sign of cavitation, often arising when suction is starved, flow is excessive, or the pump operates near its shut-off head. Water hammer involves a pressure surge from sudden valve closure, not the frequent, bubble-driven noise of cavitation, and general vibration can cause noise too but doesn’t specifically produce the characteristic pinging from collapsing vapor bubbles.