| Manufacturers determine by tests the operating characteristics of their pumps and publish the results in pump performance charts commonly called "pump curves." A typical pump curve is shown in Figure 2.
Figure 2. A typical pump curve for a horizontal centrifugal pump. NPSH is the Net Positive Suction Head required by the pump and TDSL is the Total Dynamic Suction Lift available (both at sea level).
(40KB b&w graph)
All pump curves are plotted with the flow rate on the horizontal axis and the TDH on the vertical axis. The curves in Figure 2 are for a centrifugal pump tested at different RPM.
Each curve indicates the GPM versus TDH relationship at the tested RPM. In addition, pump efficiency lines have been added and wherever the efficiency line crosses the pump curve lines that number is what the efficiency is at that point. Brake horsepower (BHP) curves have also been added; they slant down from left to right. The BHP curves are calculated using the values from the efficiency lines. At the top of the chart is an NPSH curve with its scale on the right side of the chart. | 
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