In accordance with DWA-A 143-7 [DWAA143-7:2016], the following requirements are placed on the top hat profile installation: The minimum extension into the lateral pipe, defined by the extension of the collar, must correspond to class B according to EN ISO 11296-4 [ENISO11296-4:2011], i.e. be 400 mm, but at least 150 mm beyond the first joint in the existing lateral pipe.

In the case of reconnection of lined laterals, a lower extension length is sufficient, since in this application case only the tight connection between main liner and lateral liner is the purpose of the measure. The connection angle and the connection geometry must allow for crease-free installation. Wrinkle-free installation is possible with a connection angle of 90° to ≥ 60° and only to a limited extent with < 60° to 45°. For connection angles < 45°, the top hat profile application is not recommended [DWAA143-7:2016].