This paper deals with the effect of draft tube shape on pumping capacity, as well as power input in a typical crystallizer with inner suspension circulation forced by means of propeller. The common theoretical relationship between the main factors affecting pumping capacity has been derived. Four types of draft tubes were considered including cylindrical and conical-cylindrical draft tube with inner and outer baffles. The investigations substantiating the theoretical considerations, were carried out for a wide range of independent variables: unit power input 0.1-1.5W kg(-1); d(r)/d(m) ratio 0.8-0.95; h(r)/d(r) ratio 0.15-0.6. The experimental data proved to be consistent with the theoretical predictions. The results make it possible to determine the best shape and the optimum location of the draft tube in the apparatus for generating the maximum pumping effect at minimum power input.