On Aug 16, 1:06 pm, John Rumm wrote:

Why do you need a new branch in the first place? (assuming you are only
connecting a small (ish) bore sink style waste pipe.

The new sink is quite a bit further away from the stack and the fall
over the distance means that the existing branches are too high up -
the existing drain exits the building at just below the height of the
floorboards.

Did you tell him who you were? ;-)

Nope! But I think he kept me on the line long enough to trace the
call. I'm going to phone architectural technician to see how to
proceed with regards to the (bleeding) building warrant.