In my cloakroom in my (top floor) flat, the soil pipe runs down the corner of the room, inside. It is not *quite* in the corner though and if you look at it side on it looks like
S CCCCCCCSCW S W S W S W S W S W S W S W S W S W S W S W S W S W S W J W S W S W FFFSFFFFFW
etc., where C=ceiling, W=wall, S=soil pipe and J=junction with toilet pan outlet, F=floor.
I am fitting a new toilet and would like to connect to the soil pipe closer to the wall (W). It would also be nice if I could run the majority of the soil pipe nearer the corner, so the section that must be boxed in is smaller.
So my question is, is it easy/hard/impossible/impractical to try to replace the majority of the cast iron bit with a piece of plastic piping and make the diagonal and the junction with the toilet pan outlet nearer the wall, so the bottom bit looks like:
S W S W J W S W S W FFFSFFFFFW
What are the hazards I am going to face?
Alternatively, what reasons might there be why I couldn't route the soil pipe out through the wall and outside for its breather section? How high must the breather be? Does it have to be the same size as the main pipe? How could I deal with the pipe at the ceiling level which must stay as it goes through a currently watertight and so not to be disturbed flat roof?
Any thoughts gratefully received.
Peter