I have a horizontal soil pipe running across my bathroom from the wc to the corner, where it then drops vertically in the corner of the house, straight down into the sewer outside (eg. the soil pipe contained inside the house) & is boxed in on each level (how all the houses were built around here!).
There's no vent pipe, and there's an air admittance valve sited beside the wc at high level.
Question is, I want to run a basin and shower into the horizontal section.
Using a 4 port boss, can I use the 'side' connections, or must they go in through the top? (there's not a lot of clearance under the floor boards so it would be better if they went in through the side).
Jim