The pump curve of a heating pump displays the feed rate on the x-axis and the delivery head on the y-axis. The pump curve shown in the graph is curved, dropping off from left to right.
Every possible duty point of the pump is shown on the pump curve where the dependencies are as follows: high feed rate = low delivery head; low feed rate = high delivery head.
In a heating system, a system curve emerges as a function of the system hydraulics. This curve intersects with the pump curve at a point representing the duty point of the pump.