Abstract: A connection piece (111) for a plug-in connection of a fluid-carrying system of lines for distributing drinking water within stories is formed without a supporting nipple. The connection piece (111) has in the region of an inner lateral surface of the first tubular part a first peripheral guiding surface (122) and a second peripheral guiding surface (117), arranged behind the first guiding surface (122) with respect to an insertion opening of the connection piece (111), for the second tubular part (160). A first axial extent of the first guiding surface (122) and a second axial extent of the second guiding surface (117) respectively make up each at least one sixth of an inside diameter of the first tubular part (112, 120). The connection piece (111) may form part of a fitting or a faucet and is suitable in particular for use with solid plastic pipes, for example of crosslinked polyethylene.