During the process of drinking water production using a hollow fiber ultrafiltration module, the configuration generally used is an inside-out filtration in dead-end mode. In this configuration the energy consumption is limited by outside-in backwashes. Enlarging the membrane packing density and permeability raises the permeate flow and results in an increase of the module compactness. However, this strongly modifies the hydrodynamics into the module. This study allows us to determine the pressure and velocity fields in the hollow fiber network of the modules. The geometry of the module and the membranes, the membrane permeability and compactness as well as the operating entry values such as filtration or backwash pressures and gravity were taken into account. Therefore, whatever these parameters may be, it is possible to determine the pressure and velocity fields in an ultrafiltration module. It was shown that during an inside-out filtration and for the three industrial tested module configurations the hollow fibers work in a homogeneous way +/- 0.4%. However, in the case of the backwash, a greater heterogeneity may appear. Finally, the reliability of the model proposed in this paper is confirmed by comparing its numerical results with experimental data. (C) 2012 Elsevier B.V. All rights reserved.