When a kitchen is to become a bathroom...

Aloha dear ones,

we are in the process of remodeling the attic and have the following plans:

We would very much like to convert our kitchen into a bathroom.

That in itself might not be a challenge..
But we only have one supply and also only one drain - also at about 30cm height.

We thought about enlarging the drain from 5 to 10 cm.
In addition, a substructure with a height of 12.5 cm to be able to lay supply and drain pipes underneath. Has anyone tried this before? And how does it behave in relation to the drain height? Is that physically possible?

I took the trouble to create a small 3D model and attached it to this post. The supply and the drain are located in the red circle.

Hoping that I have expressed myself clearly

Elandria

Kitchen to bathroom is definitely more difficult than the other way around, precisely because you need the 10 cm diameter of the drain for the toilet. Simply widening it could also be difficult, depending on how much wall you then have to tear open. In addition, the bathtub or shower usually have a drain at floor level, so you would have to chisel a bit. If everything is exposed, you can certainly judge that better. We once had a plumber here on this topic, who said you would have to chisel the floor a bit to get to the soil pipe and install a lateral branch there at floor level. So it would all work, it's just a matter of effort.

The project stands or falls in my opinion with the diameter of the drain pipe that runs down in the wall. If the pipe only has a diameter of 5cm, it will probably be difficult. In any case, the wall must be broken open, then perhaps the height of the drain can also be changed. If no other drains are connected to the pipe leading down, it could be that it does not have the required diameter further down either.

Thank you very much for the answers.

Opening the wall to enlarge the drain is something we cannot avoid, we agreed on that early on - But we didn’t think of something as banal as simply changing the opening height. How embarrassing... *facepalm*

In our case, we are lucky that another drain is connected, which is why we assume that we won’t have any problems with further runs in this old house. Or has anyone else experienced differently?

How about the construction? Is it even possible to make a wooden substructure at this height that can also support the weight of tiles and people? And is a height of 12.5 cm even enough?

Best regards
Elandria

So our wooden structure supports the entire house. Yes, that works, 12.5 cm could be a bit tight since the wood itself also has a diameter, so I would definitely use 6x8cm beams. In our old building, as mentioned, the floor also has to be broken up to connect the floor drain (what does "floor drain" mean, it runs almost parallel to the floor and simply requires a slope). Therefore, we are still considering if and how to implement it. It will be cheaper if everything is already prepared and exposed, and the plumber then only has to connect it.

By the way, if you open the wall, the one below must also be open, and actually the entire path to the next downpipe, because the 10 cm diameter applies to the entire length of the toilet drain. Depending on where the downpipe is, the effort is more or less.

As far as the slope is concerned, we hadn't even thought about the fact that we need more... Thanks Elina for the prompt! I will take that into account in the planning now. As for the pipe: it can be enlarged! The lines underneath allow for it, and so this fear would also be dispelled. Thank you very much for the advice so far and the valuable tips! Next station: attic -.-