Soil and waste for attic bathroom.

Hi folks.

I am fitting a bathroom in an existing attic conversion and would like a bit of advice regarding the soil and waste pipes.

I have building warrant in place but the wastes are all just shown as schematic lines to a new stack. I have had a new inspection chamber fitted and will shortly be fitting a new stack which will enter the attic through the soffit and run horizontally for 2.5m to a wc with a tee to a AAV in the eaves.

I'm fine with this soil branch but am unsure about the wastes. I would like to tee these 2 wastes (bath/shower and basin) into the horizontal soil pipe for external aesthetic reasons. Are there any regulatory or practical reasons why this is not best practice? I'm in Glasgow in case this makes any difference.

Any thoughts or advice would be appreciated.

2 inch waste pipe is enough for that

Thanks. Although the diameter wasn't my concern.

I will have one 50 mm from shower/bath and 32mm from basin. i was hoping to get thoughts on whether it was ok to connect both of these to the horrizontal branch in the eves or if they should be run to the vertical stack. I was hoping to run to the horrizontal soil to minimise external pipework.

I have been searching the forum and googling this issue and the consensus seems that it is fine to connect wastes to a horrizontal soil pipe.

Can anyone back up this theory or challenge it?

I am close to the point where I will be assembling the soil and waste and would really appreciate an indication that I'm not going to regret running these pipes this way.

Thanks

James