Question about kitchen drainage / piping

So I listened again. It will be a 70mm pipe. At the moment it is planned to be installed under the ceiling of the basement room (living space). Since the pipe still needs a slope, it will probably require a 10 cm drop ;( The pipe would then be centered in the room and 2 m away from the wall.

I asked if it could be laid in the screed, but I was told that if there is ever damage to the pipe, the entire ceiling and screed would have to be broken up.

I am not happy with the drop. I could also lower the entire room ceiling, but then I would lose 10 cm across the whole room again. Fortunately, the room height is 2.50m, but I didn't raise the ceilings just to lower them again and lose height ;(

HT-70? What exactly is supposed to be connected to it? Butcher's sink? Also the dishwasher?

By the way, a 70 pipe does not provide a 10 cm shaft. The shaft needs space, as does the pipe bracket, which usually requires 1-2 cm, and then there still have to be fittings, or the bend from vertical to "horizontal".

So we also have a few meters of water and sewage pipes laid under the screed, I don't see a problem with that. If there is ever damage, it is of course really a hassle, but the probability is quite low and it is not even about 10 meters. They are probably more afraid that they won't lay the slope correctly and then have to open everything up themselves again *g*.

a regular sink is to be drained with it. No idea why 70mm pipe. I can only pass it on as I was told.

- so what would the fall be with the 70mm pipe?
- so would HT 40/50 be sufficient for a sink?
- alternative installation in ceiling/screed yes or no?

are there alternatives I can suggest to the builder?

- so would a HT 40/50 be sufficient for a sink?

Take a look at the pipe where your sink/dishwasher currently drains. For us, it’s a 50mm pipe. The same goes for the bathroom sinks. As far as I know, a narrower pipe means a higher flow velocity, and that’s actually what you want (keyword "fat").

As I said, I am an amateur and can only pass on what was told to me. If you tell me that a 50 is also more than enough or sufficient, then I will bring it up again.