Proper design of a pumping system requires that the pump curve have to be as close as possible the system set-point curve, so that the energy used is optimal. This is achieved by control systems, in which and the combination between Fixed Speed Drives (FSD) pumps and Variable Speed Drive (VSD) pumps and the type of control to be used (flow or pressure) are involved. The objective of this work is to determine the optimal number of FSD and VSD pumps operating for each flow rate range. For this, a generic formulation is developed that allows discussing the influence of the network curve and the best efficient point of the pump provided in the pumping design solution analyzed. Additionally, the method includes analyses investment costs and maintenance costs and value the importance of these aspects in a design of a pumping system. The application of the methodology to different cases studies allows to conclude that the number of FSD and VSD pumps cannot be deduced in simple way as it is done in classic design of control system pump, but it requires a depth analysis in control modes system for do a proper pumping system design.