The CFD-code FLUENT, version 5.4, was used to analyze the flow of two test pumps of the end-suction volute type, one with a low specific speed and the other with a medium specific speed. Head as a function of flow rate at constant rotational speed is known for both, according to experiments. For the analysis of turbomachinery flows, FLUENT offers three different calculation methods: the Multiple Reference Frame technique (MRF), the Mixing Plane method (MP), and the Sliding Mesh method (SM). In all three methods, the rotor flow is computed in a revolving reference frame, whereas the stator flow is approximated in an absolute reference frame. While unsteady flow equations are solved using the SM method, stable flow equations are solved using the MRF and MP approaches. Physical approximations are not introduced by the SM technique. The unstable interaction between the rotor and stator is approximated by the steady approaches. However, the cost of the unsteady method is often 30 to 50 times more than that of the steady method. It is discovered that for flows that are far from the optimal efficiency point, the MRF and MP approaches produce entirely inaccurate flow field predictions. Because of this, the steady approaches cannot be used to predict performance in general.