Planning of wastewater downpipes

OK, understood. However: a downpipe right through the dining room is also annoying. We are planning a semi-detached house. You’re not so free in the planning there. By the way, we have several downpipes. I wouldn’t see the drainage of the bathroom wastewater as too critical if it runs 1-2m horizontally. You are definitely right about the toilet.

The bathtub drain as well as the washbasin are routed to the large downpipe near the toilet. If your bathroom is located in the middle, it could be that the downpipe runs along where a kitchen wall is planned. In this case, usually a recess is cut out on the back wall for the kitchen furniture.
If the kitchen is open, then this downpipe can be visually and acoustically clad.
The construction company usually doesn't care about internal sound insulation, the main thing is that the build is economical.

Therefore, bathrooms on the upper floor are usually planned above the building services, the WC, or a storage room on the ground floor and not directly above the living or dining room.

We are also aware of that: the bathroom on the upper floor is above the kitchen. However, we also have a bathroom in the attic, and that is planned in the semi-detached house in the middle, that is, under the gable, so that I have two equally sized children's rooms symmetrically to the left and right of the gable. Our planning is not easy for this reason alone, since I have to plan over three floors.

I would expect the architect to be able to do that. Otherwise, failed profession. And if he plans a boxing in a living or sleeping room, I would immediately ask him to work with a transparent acrylic tube.