Ok - I built a downstairs toilet a few months back - using sani-split
which is a saniflow type system - except better. Anyway - so far its
been great.
My issue relates to my possible error in ref to regulations, in the fact
I did not seek advice beforehand.
The existing soil stack, runs down the internal of the house, and is
hence in the kitchn - board up - but accessible as waste pipes access it
for the sink and washing machine.
What I have done, is run 32mm pipe underneath several kitchen cudboards
- not visable at all but accessible - and it then into the soil pipe via
a spare access point, and the other end, goes through a wall -
underneath my stairs, and into the new toilet.

Am I right, in my concerns that this breaks some sort of building
regulations?

Scott