Since the inlet and the outlet of each pump
shown in Figure 11 are at identical points in the system,
each pump must produce the same pump head. The total flow
rate in the system, however,
is the sum of the individual flow rates for each pump.
When the system characteristic curve is
considered with the curve for pumps in parallel, the operating
point at the intersection of the two curves represents a
higher volumetric flow rate than for
a single pump and a greater system head loss. As shown in
Figure 12, a greater system head loss
occurs with the increased fluid velocity resulting from the
increased volumetric flow rate. Because
of the greater system head, the volumetric flow rate is
actually less than twice the flow rate
achieved by using a single pump.
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