A quick update on this: Unfortunately, on closer inspection I have come to learn that there is a joist very close to this wall. This rules out the possibility of concealed waste pipe eve if I channelled the wall. I could only do this now if I notch the top of this joist as well as channelling the wall. I doubt anyone is going to recommend that?
I will still send the waste pipe in between these joists and keep them below floor level but will now have a pedestal basin with the waste pipe and water pipes running behind this.
I will still send the waste pipe in between these joists and keep them below floor level but will now have a pedestal basin with the waste pipe and water pipes running behind this.