A device for alternate sterile connection of a peritoneal catheter, permanently attached to a patient, to a drain tube and to a feed tube for a dialysis liquid, which apparatus comprises a shell in which a first chamber, a second chamber and a connection channel between said chambers are formed and filled with a disinfecting liquid. The chambers include respective couplings for releasable and repeatable coupling the peritoneal catheter and the drain or feed tube with the chambers in conditions of full immersion in the disinfecting liquid. This arrangement makes a tight sterile connection between said catheter and, alternately, said drain and feed tubes via said connection channel.