ᐅ Wastewater pipes either routed under the foundation slab or combined outside

We have just signed the building application documents and have a problem. The property developer says we should connect the wastewater pipes under the slab (no basement), while the building inspector says, according to DIN 1986-100, they should lead directly outside and be connected externally. The argument for routing under the slab is frost protection, and for outside routing, accessibility. Does anyone have experience or expertise with this?

Sewer pipes should run directly outside and not underneath the slab anywhere, yes!
This should be taken into account in the plans and the floor layout, yes!
Toilets should preferably be stacked vertically or placed against exterior walls, at least the drain shaft, yes.
Are you building with a general contractor (GC), not a property developer?
So, you planned the house with your GC, and they make many things possible for you, regardless of whether it makes sense or not?
Please show the plans.

However, I find your question about experience and expertise odd, since it is the expert who has that... and they did their work right here and now.

Thank you for the response. We are building with a general contractor, and they want the connection to be made under the foundation slab. Overall, we tend to agree with the opinion of the building savings contract.

There is nothing to add to ypg's contribution.
The general contractor just wants to save money, that's all.

It was similar for us. I even went to the water utility in advance, and the clerk gave us the tip to combine the sewer pipes outside. The architects would have preferred to branch them under the slab. And what happened? Just as predicted, the architect planned the sewer pipes that way.

Quote: Nothing has ever gone wrong, it’s cheaper, and if necessary, you can access everything for flushing. How often has a slab in your neighborhood been opened up just to get to a sewer pipe?

I understand both arguments and the pros and cons.

However, it will be executed as suggested by the water utility when the time comes. It costs a bit more because the trench is somewhat longer and a few extra meters of PVC pipe have to be buried.