Invert levels for rest bend that exits straight out the house?

[flanagaj]

If an internal soil pipe comes down the wall and exits the house via a rest bend, is the invert level of said waste pipe governed by the thickness of the floor build up, eg screed, 150mm PIR, 150mm concrete slab, sand blinding, hardcore? Or are those layers irrelevant by the virtue of exiting straight out the house?

 

I am also scratching my head as to how I use a rest bend and Radon barrier to hat on said rest bend when the bend radius is quite large and the Radon membrane is underneath the concrete slab.  This will mean that for the barrier hat to be sitting on the vertical pipe, the invert level is forced really deep.  I had no intention of having to run a deep invert just because of a Radon membrane.

Edited 22 hours ago by flanagaj

[Conor]

Can go any depth. What you want to do is work back from the lowest point in the system (connection to sewer, septic tank etc) and work your inverts back from there. This ensures you have enough fall from your highpoint (bottom of rest bend) to your outflow.

 

You need to ensure enough cover for you pipes. We laid our under slab waste pipes within the MOT type 3 layer. So was under all the membranes, slab etc. you don't really want the pipes in the slab.

 

Another thing to consider is, how does the pipe get through the footings? If it's in the tench pour, you want to put it in now. More commonly it would go through the trench blocks.

[Oz07]

Lower the better in some respects, like you say just dealing with a 4" hole thru membrane then not trying to make good round half a bend. You could bring it out the wall above your membrane if thats below your insulation layer and lose the pipe in the insulation. Tbf how tall is a rest bend 450mm ish? That doesn't put the invert too deep once you add insulation plus slab.