I want to buy some pipe and install this tomorrow so I can get on with my flooring. I need to check some calculations.   I was going to play safe and pipe it in 28mm copper.  Until I realised I don't have a drill bit to drill a large enough a masonry hole for 28mm.   So I am looking for the exact "rules" for the D2 discharge pipe.  A quick gogle finds this, for NI http://www.buildingcontrol-ni.com/assets/pdf/P1994.pdf  I would have thought it was the same rules in all p