What must a centrifugal pump do before it can operate properly?

A centrifugal pump must have its impeller fully submerged under water before it can operate properly because this ensures that the pump can effectively create the necessary suction to draw water into the system. When the impeller is submerged, it can generate the centrifugal force that lifts the water and moves it through the pump and into the discharge line. If the impeller is not submerged, air may be present in the pump, preventing it from priming and thus causing it to fail to move the liquid as intended. This submerged condition allows the pump to develop the required pressure for efficient operation.

While being connected to a power source is important for the pump to function, it is not sufficient on its own without ensuring the impeller is under water. Additionally, regular maintenance is crucial for long-term pump performance and reliability, but it does not directly affect the pump's immediate ability to operate upon starting. Partially filling the pump with air would impede its ability to create pressure and flow. Therefore, having the impeller fully submerged is essential for proper operation.