What would cause a pump to deliver less than its expected rate of discharge?

When examining the scenario where a pump delivers less than its expected rate of discharge, a clogged impeller is a key factor that can significantly restrict the flow of fluid. The impeller is the rotating part of the pump that transfers energy to the fluid, and any obstruction – such as debris or buildup – can impede its ability to effectively push fluid through the pump. This reduction in flow can result in the pump not meeting its designed performance specifications.

While other factors like worn-out bearings, a faulty motor, or a closed valve can affect pump operation, they primarily impact either the mechanical performance or the power supply to the pump rather than directly constraining the flow capacity. For instance, worn bearings may lead to vibration or noise, and a faulty motor can lead to a complete failure to operate. A closed valve would simply prevent fluid from passing through, but it would be a deliberate action rather than an issue with the pump mechanism itself. In contrast, a clogged impeller directly obstructs flow, making it the most pertinent cause for reduced discharge rates.