Abstract: Device for making potable water out of water contaminated by a.o. chemical, biological and nuclear pollutants, as well as by pathogenic bacteria, viruses and normal solid particles, said device being provided by a perforated plate filter, connected to a finer filter in turn coupled to an ultrafilter directly followed by a hyperfilter without interposition of a buffertank and an activated carbon filter, a control device being provided at the ultrafilter's entrance controlled by a pressure switch at the ultrafilter's exit. The control device keeps the pressure at the exit of the ultrafilter approximately constant.