Venting Horizontal Waste Stack for new Upstairs Bathroom

[Mbmac]

I am fitting a new upstairs internal bathroom and running a soil stack horizontally to join the existing mains sewerage which is located internally at the back of the house and has another WC running into it at that point. This is the first time the property will have an upstairs toilet. My question is how should I vent this horizontal stack?

[welsh brickie]

you will need to fit a T piece at the toilet, and add a bend to make the pipe vertical, normally in a corner, Then vent the pipe by adding a durgo valve. The pipe can then be boxed in to hide it.

[Mbmac]

How far away can I T to add vent, would it be ok 4 meters from WC, we could put it in the roof cavity of single storey extension if 4 meters away from wc would be ok?