how deep drains should go under the floor/hardcore?

[vovan]

I assume drains should go below hardcore. What would be minimum depth? I'd like to get main drain (that will collect all waste from first floor) under the floor in a garage, then it will need to go under approx 3m wide extention. To plan opening depth and size in a foundation, I need to know what minimum starting depth is.

thanks.
v.

 

[noseall]

The drain is positioned, depth wise, where the falls dictate.

Ideally yes, either below or even in the hardcore layer.

On some very shallow drains we once fitted the drain had to (partially) pass through the insulation layer and it was a mare!

Where drains are exposed i.e. not under buildings, building control recommend a minimum of 300mm cover.

 

[vovan]

thanks. will open an inspection chamber to see depth at which I should connect and will see what depth at entry point in the garage can be. hopefully in or under hardcore. with this I'll have something to show building inspector.