quote; I've never done this - any tips? Anything I need to know about when making good the concrete afterwards e.g. dpm, rebar?
The best tip we can give you is related to your first five words in the above quote. You have NEVER done this before and NOW is not a good time to start, unless you first take a course in Plumbing 201, (Plumbing 101 just deals with minor repairs). Fail to do this and you will create a system that will hound you for the rest of its life. The first step is to take your drawing down to the city building department and have it approved then get a building permit for it.