off against the saddle pipe 7 by a seal after the front opening of the formwork pipe is sealed off the entire cavity can be grouted the formwork pipe with the lid to seal the front opening could be removed again after the grouting mortar 8 had hardened the detachable connection between the connecting pipe 14 and the sheathing 4 in this embodiment the transition pipe 15 is illustrated in fig5 as detail v of fig4 at a larger scale on its sheathing end the connecting pipe 14 has an inner flange 23 to which an outer flange 24 of the transition pipe 15 abuts from the outside the outer flange 24 can be welded to the end of the pe transition pipe 15 the friction locked connection between the transition pipe 15 and the connecting pipe 14 is ensured by an axis parallel screw connection 25 which acts against a loose flange ring 26 the installation of the sheathing is considerably simplified by the flange ring 26 which can be attached from the outside the force of the screw connection bears on the welded on pe flange 24 via a ring 27 that is made of an elastic material for example rubber or plastic in this way constraint tensions due potentially occurring angle errors or movements are avoided and.