Abstract This paper considers the well-documented theory for the design of sedimentation tanks. The difference in this treatment is that a numerical model is used to do the necessary calculations for the limiting flux and the equations to do this are put in a dimensionless format. The model for a cylindrical settler is extended to the case of a conical settling geometry. It is shown that the conical settler can handle a wider range of solids loading. Finally, calculations are reported to estimate the characteristics of batch settling experiments for conical settlers and the results are compared with experimental data.