Drainage installation problems

[blackie]

I have currently got builders working on my extention but they are just doing the excavation, footins walls + roof etc.
Somehow i have been landed with the task of drainage, plumbing and wiring, it is the drainage where i am a little lacking in experience I would appreciate any helpfull info about rate of fall under floor, outlets(boss)
to cloaks/wc ,kitchen and utility,and also picking up outside rainwater as i do not know about traps and bends etc.
Thanks

 

[masona]

Normally a fall ratio of 1:40,regarding outlets,traps & bend pop down to your builder merchant for a catalogue on drains/rain system as there're many ways of doing it.