Unfortunately he wants one just above the sink.If you’ve no windows/door openings at the back then you can get away with a stub stack
To be honest I don't know, in fact I think/hope it's not in use. I've poked it with a stick and it's just mud. But it does have a run of pipe going to it(couldn't get the stick in that far though) - why would someone do that if it's unused? The land also slopes downwards from the edge of the property in that direction.You show a “Y” connector for the new 45 degree connection into the existing inspection hatch, what’s the purpose of the other drain leg which seems to terminate under the edge of the washbasin?
View media item 20830
Gotcha . Can't see how I can go any straighter than this, without a new inspection chamber.Keep pipe runs as straight as possible; you are allowed one change in direction up to 45 degree, go greater than that or introduce another bend & you will need rodding access from the other end. I’m not sure why you’ve introduced that 45 degree bend at the bottom of the rest bend but I would loose it if possible.
View media item 20829