Floor plan planning shortly before submitting the building application

A purposeful question in this regard would be, for example, whether it is now common practice to include the house connection box in the execution plan or not.

I thought I had answered that: one energy provider installs its meters and everything related inside the general power distribution box, another installs its own black box next to it, and the third places a red box on the floor. You simply cannot include that in the plans without having agreed on it. It doesn't matter legally afterward who the customer is, technically/logistically it is nonsense to let the builder clarify that. You don't delegate anything to laypersons that must integrate with a handful of other specialist trades. The general contractor could have told the energy provider: "The cave painting on the construction site is what counts." But if the general contractor already knows this is the first and last time with the shell builder, then he should kindly be on site on such critical days. Then, in the interest of limiting damage to their own image, they ensure that everything runs tip-top from then on.

I just had Hansgrohe confirm to me that a 20 mm line is required.

Do they perhaps have a nice PDF with the specifications in the download area?

Do they perhaps have a nice PDF with the specifications in the download section?

Only that the connection thread is G 1/2 and the connection size is DN15.

If I may ask, where did you get the 20 meter cable from? Someone must have recommended it to you or you must have read it somewhere. If Hansgrohe doesn’t specify anything, then it is probably indeed difficult.

Only that the connection thread is G 1/2 and the connection size DN15.

Without any mention of a reducing piece, I wouldn't conclude from 15 that 20 is indicated beforehand.

Without mention of a reducer, I wouldn't conclude from 15 that 20 was intended before it.

That's exactly what I mean! How can I go all out somewhere when one says this, the other says that? I simply have no idea about this!!

I will hire a plumbing expert who will take the whole place apart. I can't get any further otherwise.

Who initially spoke of a 20 mm pipe? As mentioned, there is a DN15 connection piece in the HansGrohe drawing, so a 20 mm pipe would actually be strange. HansGrohe saying that on the phone is of course confusing, but maybe there was no expert on the phone?

Talk to the expert, an additional sanitary expert will probably arrive too late anyway.