A chilled water pump is cavitating. Which of the following is the most likely cause?

• A. Air in the suction line
• B. Water leaks through the mechanical seals
• C. Excess downstream pressure
• D. Overheating motor

Answer: (B)

Cavitation happens when the pressure on the pump’s suction side falls below the water’s vapor pressure, causing tiny vapor bubbles to form that collapse as they move to higher pressure regions. The most likely cause here is air in the suction line. Air reduces the effective suction pressure and makes it easy for vapor bubbles to form, leading to cavitation and the associated noise and wear. Water leaks through the mechanical seals don’t create the low-suction condition inside the pump, so they’re not a driver of cavitation. Excess downstream pressure changes the head the pump must deliver but doesn’t by itself produce the low suction pressure needed for cavitation, and an overheating motor is a separate electrical/mechanical issue, not a cavitation cause.