The primary disadvantage of a single-stage centrifugal pump is that the head at which it will effectively pump against is:

A single-stage centrifugal pump is designed to deliver fluid at a specific pressure, known as head. The primary disadvantage of this type of pump is its inherent limitation regarding the maximum head it can achieve. Due to its construction and design, a single-stage centrifugal pump can only effectively generate a certain amount of pressure before it starts losing efficiency.

This limitation arises from the pump's single impeller, which can only lift fluid to a certain height based on factors such as the pump's speed and the design of the impeller. When the required head exceeds this capacity, the pump may not be able to lift the fluid effectively, which can lead to issues such as cavitation or inadequate flow rates.

In contrast, multi-stage centrifugal pumps, which have multiple impellers, can achieve much higher heads by adding additional stages that build upon the pressure provided by the previous stage. However, this question specifically concerns single-stage pumps, making the limitation on head one of their most significant disadvantages. This characteristic is important for anyone involved in the selection and operation of pumping systems, as understanding the application’s head requirements is critical for choosing the right pump.