Hello There, Can you please let me know what you think is the best design for installing new drainage pipes for a new kitchen extension -just starting being built from the founds. I've read through the Building Regs (H section) but cannot find detail. My dilemna is ....Should the waste pipe be run outside underfloor to a gully? -to then run to the new inspection chamber or above floor height outside in say a 50mm plastic pipe?
Also thinking about a future washing machine, what is the best way of integrating the waste from the w/m to the same drain line?
New build is an opportunity to do away with pipes going through walls and running outside to a gully where they can freeze, etc.
I have a 4" drainage pipe coming up under my sink. It takes a bit of space in the cupboard, but then offers total flexibility for connecting things up (including a toilet !).
Make sure you connect in swept bends if possible (it would cope with solids), 2 x 45 degree instead of 1 x 90 degree is OK. My BCO make me change it when I said it may contain semi-solids from a waste disposal unit.
You can get rear entry gullies that accept 4" pipe from behind, which are a half-way house, but still risk the gulley blocking up.
Sometimes you want a gulley below an outside tap - I put one in on a separate line that is nothing to do with the sink, even though it is on the other side of the wall.
If you insist on going through the wall for some reason, you can connect the various appliances up (32mm or 40mm) to a 40mm or 50mm drain line, but may get various gurgles from the plugholes as other things drain. Or separate pipes through the wall, but that looks a right mess.
Simon.
