What is cavitation, and how does it affect pump performance?

• A. Formation and collapse of vapor bubbles due to insufficient suction; causes loss of pumping efficiency and damage.
• B. Bubbles in the oil causing lubrication problems; reduces wear.
• C. Air pockets in the discharge line; cause smoother flow.
• D. Formation and collapse of vapor bubbles due to excessive suction; causes increased efficiency.

Answer: (A)

Cavitation happens when the liquid at the pump inlet experiences a drop in pressure below its vapor pressure, usually from insufficient suction or very high flow velocity. In that low-pressure region vapor bubbles form. As the liquid moves to higher-pressure areas inside the pump, these bubbles collapse violently, sending shock waves and microjets that damage impeller surfaces and disrupt the flow.

That collapse drains energy from the liquid and creates flow instabilities, so the pump can’t develop its rated head or deliver the expected flow. You’ll also hear louder operation and see vibrations as the bubbles form and collapse repeatedly. Over time, the erosion from cavitation can wear away impeller material and bearings, shortening the pump’s life.

The other descriptions don’t fit cavitation: simply having air pockets or bubbles elsewhere in the system isn’t the same process, and cavitation is tied to a pressure drop—not to “excessive suction”—and it does not improve efficiency.