System characteristic

The system characteristic describes the connection between volume flow-rate and pressure loss in a given pipe system.

The system characteristics will normally have the shape of a parabola. This means that the pressure loss in a system is an increasing quadratic function of the volume flow-rate.:

H = K x Q2.
In practical terms, this means that when the volume flow-rate is decreased by one-half, the pressure loss is reduced by 1/4.
The size K expresses the resistance in the system. The higher the resistance, the steeper the parabola becomes. The system characteristic can be determined from pressure loss calculations. At existing systems, it can be determined through measurements.

The system characteristic is used together with the pump’s performance curve for dimensioning and correct pump selection.