Can I tee into soil vent in loft?

[Rzzrmeanr]

My stack appears to vent into the loft, presumably using an air admittance vent, as there are no odours coming from it until you lift off the vent. Can this just be teed into with a new branch waste pipe (inc. toilet and shower waste) or would I have to extend the pipe to the outside?

 

[joni os]

Yes,provided you extend vent above spill level of all basins etc. connected to it.

 

[Welder]

Hmm. Your stack also needs to vent gases which build up not just let air in. Is there any other soil stack connected to your system that has an open vent? Perhaps above the tiles?

 

[AWheating]

Teein in will be fine. No need to open vent as long as aav is above spill level and ventilated but may be the best option if you can fit a tile vent away from any openings.