PUT THE ROUND, IN THE SQUARE

Not like this:
This construction calls for a red card. A rectangular recess for the entry of corrugated pipes is definitely not watertight, as moisture and radon gas can pass through the gaps and into the building. If we were refereeing, we would blow the whistle straight away.

A better game plan at the outset would have saved quite some trouble. But never mind, Hauff-Technik has a solution: Flange with WRD-System.