The meaning of differential pressure

• A. Difference between the inlet and the outlet of the pump
• B. Pressure drop across a valve
• C. Pressure difference between tank and atmosphere
• D. Difference between upstream and downstream along the line

Answer: (A)

Differential pressure is the difference in pressure between two points in a system. For a pump, this is the pressure at the outlet minus the pressure at the inlet, showing how much pressure the pump adds to the fluid. This inlet-to-outlet pressure rise is what we measure as the pump’s head and overall performance. While differential pressure can describe other things—like the drop across a valve or the difference between upstream and downstream along a pipe—the common, most direct meaning in the context of a pump is the pressure change from inlet to outlet. The pressure difference between a tank and the atmosphere isn’t the same kind of differential pressure used to gauge pump performance.