What does the presence of air bubbles in a water pump's output suggest?

The presence of air bubbles in a water pump's output suggests that there is cavitation occurring. Cavitation is a phenomenon that can happen when the pressure in a liquid drops to below its vapor pressure, creating vapor pockets that can collapse violently when they flow into higher pressure areas. This can cause not only air bubbles but also significant damage to the pump impeller and other components.

When there are air bubbles visible in the output, it indicates that the water is not flowing properly, which can be a direct result of cavitation. This condition leads to inefficiencies in the pumping process and can strain the system, possibly leading to equipment failures if not addressed. Understanding this helps operators recognize signs of potentially harmful conditions in their pumping systems, which can facilitate timely maintenance or adjustments to prevent further issues.

In contrast, the other choices do not align with the implications of air bubbles. Normal temperature or optimal function would not typically present with air bubbles, nor does the presence of bubbles indicate water contamination by itself.