Hi I'm not much of a diy expert particularly on drainage. Had this drawing done a few months ago and now I have a waste for sink from plumber and the gutter from roof of extension (see photo descriptions). I had to get a new builder to finish off as original one dug hole and has since not answered calls or returned messages. New builder has said to ask architect if I need a new IC for waste water and whether he would accept a gulley with grille as there is an inspection chamber right by it one side (see photo with pipes), and an inspection chamber a couple of feet the other side where waste meets sewer run from neighbour next door and flows off to wherever. New Builder said he would cut out section of clay extg sewer pipe and use plastic with connection to gully.
Can I get some advice on whether this is possible, or if i should have a new IC? If I do what would best option be?
