What conditions must be met for a centrifugal water pump to be correctly primed?

For a centrifugal water pump to be correctly primed, it must be full of water and all air must have been purged out. This is essential because centrifugal pumps rely on the presence of liquid rather than air to create the necessary hydraulic action for efficient operation.

When the pump is filled with water and free of air, the liquid can effectively transfer the energy generated by the impeller, allowing for proper flow and pressure development. If there is air trapped in the pump casing or suction line, it can lead to cavitation or a significant loss of efficiency, causing inadequate pumping performance or potential damage to the pump itself. Proper priming ensures that the pump is ready to operate effectively from the moment it is started.

Other conditions, like lubrication of the pump seal or operating at maximum discharge pressure, are important for the long-term operation of the pump but are not prerequisites for initial priming. Additionally, while having some water in the pump is beneficial, merely being partially filled does not ensure effective operation, highlighting why complete filling and purging of air is critical.