The expansion of operational capabilities of existing storage hydropower plants is currently being investigated at the Institute of Fluid Mechanics and Hydraulic Machinery (IHS) within the project “Flexibilization through the Upgrade of Existing Hydropower Plants to Pumped Storage Operation.” Specifically, the project examines, using a real power plant as a case study, the conversion of an existing Francis turbine into a pump turbine by replacing as few individual components as possible. The aim is to identify the associated opportunities and challenges of such a retrofit. However, converting a turbine into a pump turbine in the same installation configuration generally results in a significantly increased risk of cavitation, particularly during pump operation. The hydraulic design of the pump turbine is therefore carried out using optimization methods supported by computational flow simulations, based on the in-house design system dtOO developed at the institute. The objective is to simultaneously consider both turbine and pump operation across multiple operating points, as well as the corresponding heads for energy generation and pumping, within the optimization process. This also includes minimizing the risk of cavitation. We would like to thank VERBUND AG for providing the geometric data of a representative plant, and KSB Foundation for their financial support of the project.