Abstract: A device for connecting a branch pipe (54) on a fluid-transporting piping system (C). The device (B) includes a support portion (12) on a wall of the piping system (C); a piece (28) for connecting the pipe (54); a perforating member (20) provided with a cutter (70) for perforating the wall (10) of the pipe and a cylindrical portion (71) mounted atop the cutter whereof the outer face (60) is smooth. The device further includes a shaft (16) cylindrical in shape along an axis (51) which receives the perforating member (20) and wherein the perforator can be displaced by screwing to pass from a position perforating the wall (10) to a retracted position inside the shaft (16). A seal (E, 30) is disposed between the shaft (16) and the perforating member (20). The support portion (12), the connecting piece (28), the shaft (16) and the seal (E) are made integral by moulding or overmoulding, and the seal is supported on the outer face of the perforating member (20).