Is this secondary construction cost calculation realistic?

Is explained under the section Drainage.

However, the work is carried out by myself. So it is basically considered "only" as a buffer.

Is explained under the drainage section.

However, the work is done by myself. So it is basically considered "only" as a buffer.

I don't see it in #20, but okay. If you say so...

I don't see that in #20, but alright. If you say so...

I had probably called it a sewage connection.

I had probably called it a sewer connection.

That is something different.

The rainwater is also directed into a sewer system here.

For example, I don't see anywhere where the connection of downpipes to the rainwater shaft is addressed.

The general contractor said that we don't have a rainwater shaft. The development plan states: The rainwater from the roof surfaces must infiltrate via near-natural infiltration systems, as long as it is not used as service water.

Or does it always have to be there??