A filtration unit (1) comprising a support (10) arranged to receive a plurality of filter cartridges (11,11′), the support configured to allow a displacement of the cartridges between a working position (70), in which a first filter cartridge (11) is arranged with own inlet/outlet apertures (71′,71″) in communication with a fluid inlet and outlet line portions (7,8), respectively, and at least one standby position (75) configured for receiving a respective second filter cartridge (11′), an exchange mechanism (12) configured for causing the displacement of the cartridges between the at least one standby position and the working position, a differential pressure sensor (80) configured for measuring a pressure drop through first filter cartridge arranged in the working position and for generating a differential pressure signal (286) responsive to the pressure drop, a control unit (90) configured for receiving the differential pressure signal (86) and for providing an actuation signal (287) of the exchange mechanism, a program means resident in the control unit (90) and configured for generating the actuation signal (287) when the differential pressure signal indicates a pressure drop value exceeding a predetermined lower threshold value. This way, it is possible to arrange a clean filter cartridge in the at least one standby position, ready to be displaced to the working position in replacement of first filter cartridge, and the at least one second clean filter cartridge is transferred to the working position upon exceeding the differential pressure threshold value, remarkably limiting filter maintenance time and costs in a complex fluid distribution network.