Two modular side channel pump models have been investigated both numerically and experimentally. For both modular designs, different side channels and impellers could be studied, with the aim to get information about the influence of the different geometries on the performance and the inner flow phenomena of the pump. By understanding the geometry influences, statements about the design process of the pump are possible. Changes of the geometry of the side channel or the impeller affect the flow in both components. This means that the geometrical dimensions must always be related to each other, in order to make statements about influences of the geometry on the characteristics. Thus, various geometrical configurations are setup, their sizes in industrial pumps are indicated and their influence is investigated by simulations. To evaluate the gained numerical data, it is important to understand the influence of mesh and simulation setup on the results. Therefore, a grid study was conducted and additionally the turbulence model was varied. In this paper, two parameters are focused on: these are the side channel height to the blade length (h/l) and the depth of the side channel in relation to the width of the blade (t/w).