Water Distribution Grade 1 Certification Practice Exam

What causes pump cavitation?

1. A clogged suction line or pump being above the waterline

2. A high-temperature environment

3. Low viscosity fluids

4. Insufficient lubrication

The correct answer is: A clogged suction line or pump being above the waterline

Cavitation in a pump occurs primarily due to conditions that lead to a drop in pressure at the pump inlet, which causes the liquid to vaporize and form bubbles. When these vapor bubbles travel to a high-pressure area within the pump, they collapse, creating shock waves that can cause significant damage to the pump components. The situation described in the correct choice, where there is a clogged suction line or the pump is positioned above the waterline, can impede the flow of liquid into the pump. This results in a reduced pressure at the pump intake, making it possible for vapor bubbles to form, leading to cavitation. It is crucial for the pump to have an adequate supply of liquid to operate effectively and avoid such damaging conditions. Other factors listed, like a high-temperature environment, can also impact pump performance but do not directly cause cavitation as defined by low pressure implosion. Low viscosity fluids can change how the liquid behaves within the pump but are not a direct cause of cavitation. Insufficient lubrication primarily affects mechanical components rather than fluid dynamics related to cavitation. Thus, the immediate physical setup and flow conditions are foundational to understanding pump cavitation, making the first option the most relevant.