What happens to the discharge pressure of a pump when the flow decreases?

When the flow in a pump decreases, the discharge pressure typically increases. This relationship is rooted in the fundamental principles of pump operation and hydraulic systems.

In a centrifugal pump, for instance, as the flow rate decreases, the pump operates more efficiently at a higher pressure. Pumps are designed to create a certain amount of pressure against the resistance of the system they're working in. When there is less flow, the pump can more effectively increase the pressure at the discharge side because there is less volume of liquid being moved through the system.

This phenomenon can also be explained in terms of the pump's characteristic curve, which illustrates how the flow rate and head (or pressure) are interrelated. As flow decreases, the head developed by the pump increases until it reaches a certain point determined by the pump's design and the system's characteristics. Thus, in simpler terms, with less liquid moving through the system, the available energy from the pump is concentrated, resulting in higher discharge pressure.

Understanding this relationship is crucial for proper pump selection and system design, ensuring reliability and efficiency in water distribution systems.