The liquid flow in a porous medium is considered for the axially-symmetric case. The filtration efficiency is estimated for filters of two possible geometries: cylindrical and radial ones. The aim of our work is to identify the characteristics of hydrodynamic flows in a porous medium filling the radial filter. In particular, we calculate the filtration coefficient, that is, the relation of the initial impurity concentration to the final one. We consider the hydrodynamic equation in a porous medium, taking into account the generalized Darcy law. In addition, the effect of transverse diffusion due to the flow around the filling grains is considered. Finally, we consider the filtration coefficient for two filter geometries: cylindrical and radial ones.