Abstract: The invention concerns a process for leak proof connection of branch lines such as house lines (1) to main lines such as rehabilitated sewer pipes (2). A lining hose (4) with a flat textile material such as nonwoven fabric, woven cloth, knit fabric, mesh fabric or laminate, which can be soaked in curable liquid resin, is introduced into the feeder line before or after soaking with a resin and its other, collar-shaped expanded end is bonded in the inside of the main line by means of a ring-formed fitting (5) to form a leak proof seal. The ring-formed fitting (5) consists of thermoplastic (7) on one side and of a flat textile material (8) such as nonwoven fabric, woven cloth, knit fabric, mesh fabric or laminate on the other. The ring-formed fitting (5) is welded with the inner thermoplastic surface (6) of the main line, while the flat textile material (8) of the ring-formed fitting (5) is connected with the collar-shaped, expanded end of the lining hose (4) by gluing.