Hydraulic machines with special features include single blade pumps. They are used for pumping liquids containing large solids in the chemical and food industries as well as in wastewater treatment plants. Since the transfer of mechanical energy from the shaft to the liquid is provided by a single blade, its design must be given proper attention. As with any turbomachine, the design proceeds in an iterative cycle that includes CFD simulation and experimental verification of the prototype. The issue of CFD simulations will be addressed in this article. This is because the single blade impeller is asymmetric, which will be reflected in the design of the computational mesh, the calculation method, the evaluation and the comparison with experiment. In this paper we will summarize our experience with different types of solvers, meshing methods as well as stationary and transient flow models.