Which plumbing component’s size can directly affect the efficiency of a sewage pump?

The size of the discharge pipe is crucial for the efficiency of a sewage pump because it directly influences how effectively the pump can move wastewater away from the source. If the discharge pipe is too small, it can cause restrictions that lead to increased friction and back pressure, reducing the pump's performance and potentially causing it to work harder or overheat. Conversely, if the discharge pipe is appropriately sized, it minimizes resistance, allowing for smooth flow and ensuring that the sewage pump operates at its optimal capacity.

Considering the other options: the supply line is primarily responsible for bringing water to fixtures rather than removing waste, so it does not impact sewage pump efficiency directly. The drain pan serves a different function by collecting condensation or spills rather than affecting sewage transport. The pressure tank is related to water supply systems and maintaining pressure in those systems, rather than affecting the sewage pump's operation. Thus, the discharge pipe is the component whose size has the most significant direct impact on the performance of a sewage pump.