When predicting the behaviour of a proposed capillary barrier, it is possible to utilize either the experimental measurements or the numerical modelling. Results of tipping trough modelling of a capillary barrier are used to study the reliability of numerical modelling. The required hydromechanical parameters of the capillary barrier layers are determined and used for the numerical repeating of the tipping trough experiments. The results are presented and discussed.Subsequently, the paper studies the problem of capillary barriers efficiency. A criterion is introduced that makes use of soil-moisture retention data in order to predict the efficiency of a capillary barrier. Hysteresis of retention curves of the applied materials is studied and its effect on the efficiency is discussed.