The following requirements are placed on the top hat profile installation:

Defective connections (gap between the end of connecting pipe and the main pipe, break (pieces of lateral pipe visibly displaced, missing pieces of lateral pipe wall)) must be repaired / pre-profiled beforehand by milling / filling robots to ensure the required shape is maintained. If cavities are formed in the connection area, they should be grouted in advance. Under these boundary conditions it must be checked whether the additional use of a top hat is still technically and economically reasonable.

The collar width (rim of collar) to be executed depends on the nominal width of the main sewer (see table) and must overlap at least 50 mm in the main pipe.

The thickness of the collar must not be less than 3.0 mm in the cured state. After completion of the measure, the clear diameter in the main pipe must not be restricted by more than 2% or 6 mm, whichever is greater [DWAA143-7:2016]. The transitions between the collar and both the main and lateral pipe should be smooth.