Which of the following statements about centrifugal pumps is NOT true?

Centrifugal pumps are indeed widely understood to be one of the simplest types of fire apparatus pumps due to their straightforward design and operation. They work by converting rotational kinetic energy, typically from an impeller, into hydrodynamic energy. This efficiency and simplicity allow for easy maintenance and operation, making them favorable in firefighting applications.

The statement regarding the influence of the pressure of incoming water on discharge pressure is critical. Discharge pressure in centrifugal pumps can indeed be affected by variations in the incoming water pressure, showcasing how external conditions impact pump performance. The pump's design and operational parameters establish a relationship between these pressures, emphasizing the importance of understanding system dynamics.

Furthermore, the speed of the impeller plays a crucial role in defining the pump's capabilities. Higher impeller speeds generally result in increased discharge pressure, making this relationship essential for effective pump operation.

Hence, the assertion that centrifugal pumps are the simplest type of fire apparatus pumps is true, reflecting the operational characteristics and benefits that these pumps provide in firefighting scenarios.