Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

What typically indicates that a pump is cavitating?

1. Constant vibration

2. High-pressure readings

3. Pinging or 'rocks bouncing' sounds

4. Decreased flow rate

The correct answer is: Pinging or 'rocks bouncing' sounds

The occurrence of pinging or 'rocks bouncing' sounds is a key indicator of cavitation in a pump. Cavitation happens when the pressure in the pump drops below the vapor pressure of the liquid, leading to the formation of vapor bubbles within the fluid. As these bubbles travel through the pump and enter higher-pressure regions, they collapse violently, creating shock waves. This collapse can produce distinct sounds that resemble pinging or the noises made by rocks bouncing, which are often described in operational contexts to indicate cavitation. While constant vibration can be associated with pump issues, it is not a definitive sign of cavitation specifically, as vibrations can stem from various mechanical problems in pumps. High-pressure readings would typically indicate that the pump is functioning correctly, whereas decreased flow rate might occur due to a range of issues, including blockages or other operational inefficiencies rather than specifically indicating cavitation. Therefore, the sounds made during cavitation are the most direct and observable indicator that this condition is occurring within a pump.