Thanks for your reply, the pipework is indeed quite old, i assume 70s/80s going by the bathroom. I think I could achieve the fall internally but I really want to avoid boxing in if I can.
i may be best starting out with a completely new horizontal section and work from there.
basin waste on...
I'm hoping for a little bit of guidance
I have 2 bathrooms side by side
The left bathroom's toilet connects to the main soil stack and has its own vent (red)
the right bathroom has a soil pipe connected to the main stack (blue)
I want to move the toilet to the left hand side of the room - i...