System Characteristic Curve

It was established that both frictional losses and small losses in piping systems were proportional to the square of the flow velocity. As flow velocity is directly proportional to the volumetric flow rate, the system head loss should be directly proportional to the square of the volumetric flow rate. From this association, it is possible to build up a curve of system head loss versus volumetric flow rate. The head loss curve for a usual piping system is in the shape of a parabola as shown in figure below.

Figure: Typical system head loss curve