Below Ground Soil Pipes on Self Build Bungalow

[umiq88]

Just started gound work on self build bungalow and wondering best way to do below ground soil pipes.

For toilet I was going to go straight down through slab and out through deadwork into a manhole. I will work out falls from manhole and set the height of the waste water system as required.

For sinks/baths/shower etc I was going to use 40/50mm through the slab/deadwork into a back inlet gulley trap -> manhole -> grease trap -> waste water. Wondering is the height of these pipes critical or is it adjustable.

I've attached a plan for reference.

 

[Last Plumber]

This Link should take you to Doc H which tells you most things re-regs that you should follow.
I think it is the most up to date but check it yourself before you use it.

 

[umiq88]

Thanks yes I've seen that but it doesn't give any guidance for ground floor that I can see.