In a centrifugal pump, what happens to the head if the discharge increases?

In a centrifugal pump, an increase in the discharge flow typically results in a decrease in the head generated by the pump. This relationship is based on the characteristics of pump performance, which are often represented in pump curves.

As the discharge flow rate rises, the system curve also shifts, reflecting an increase in system resistance due to friction losses and other factors. Since a centrifugal pump operates by converting rotational energy into kinetic energy, as the flow rate increases, the available energy for creating pressure (or head) is often reduced because the pump reaches its best efficiency point. This happens because the impeller velocity and energy imparted to the fluid cannot overcome the increasing resistance without a reduction in head.

Understanding this principle is crucial for wastewater operators, as managing flow rates and system pressure is vital for efficient operations and maintaining the integrity of the overall wastewater treatment process.