Routing internal soil stack

[gnvqsos]

I plan to put an ensuite wc in an attic room,with an internal soil stack capped with an air admittance valve.I could take the pipe through a wall ,just below the eaves,joining the existing soil stick there.I would prefer to pass the pipe through the bathroom ceiling(below) and then join with the existing WC waste.

I would be grateful for any advice you can give please.

 

[Hugh Jaleak]

Keep number of bends to a minimum in the wet section, and my preference would be to join to the existing stack externally, on a vertical section.

Joining internally to a horizontal section could cause a noise issue, and may well cause problems with the current W.C. as the contents of the new pan hit the horizontal pipe it could force air and/or effluent back through/into the existing pan. I would be surprised if Building Regs would allow such a setup anyway.