Ah right there, new here. I'm putting in a 16kw boiler stove in my house, with a vented (seems to be a fighting point on plumbing forums) cylinder. Want to do as much pipe work as i can, guy that came out to give a price to do all/part of the job aint got back to me with numbers (2 weeks now) and need to get pipes through as holding up bits of the job. I think he said no more than 3 metres horizontal pipework for unvented if they would sign off stove for building regs. The stove is 5ft from wall to the left off it, i need to go through this wall upstairs to get to cylinder cupboard. So can go straight up into bedroom then horizontal with one 90 degree then back 3ft and through the wall straight into cylinder cupboard, or is it as well to go diagonal up from the stove down stairs instead of having the 90 degree bend upstairs? Was thinking in 28mm copper pipe (upstairs is having a false floor down (4 inch kingspan so can hide pipes easily if needed) Have building inspector here as weve put an extension on but not bothered about having it signed off as we wont be moving, it just needs to be safe. Many thanks.