Abstract: A water purification through-flow device which comprises a cylindrical shell which is divided lengthwise into two or more sectors, separated from each other by partitions, with a cover fitting one end of the shell, in which cover there is provided an inlet for water which is to be purified. Depending on the number of sectors, the outlet is provided in the same cover if there are two sectors, and in the other cover if there are three sectors: the water flowing through each of the sectors one after the other. The individual sectors may contain the same purification substance, or different sectors can contain different ones. There may be provided mechanical filtration means for the water passing through the device, and there may be provided means for closing the various sectors during storage.