Ensuite smell - 3 plumbers cannot diagnose/fix..Please help

[DeltaT2]

Yup, I'm with 'doitall' crack or pin hole in the WC, I've seen it a few times with cheap sanitary ware.

 

[seanmac30]

It`s the aav - if the pipe was vented to open air it would work

This was my next thought but I want to be sure that is it before going putting a whole in my roof. As we don't use the main bathroom very often, I wonder could I test the idea by venting into the bathroom with the window open (window is right beside the loo and AAV). I know it won't be the same as venting to the outside but could it work??

If you do a Heath Robinson job with some tumble dryer hose and duct tape - you will be able to seal round the pipe and the window - and do a test for several days just watch the duct tape residue. You don`t necessarily need to go through the roof to vent - you can go through the wall and up the outside - if it`s unobtrusive . I just don`t like AAv`s because they only deal with neg pressure - Drains are subject to positive pressures too -

Thanks to everyone that provided advice. It was the positive pressure of fumes percolating into the pan water and diffusing into the bathroom. Just got rid of AAAV and vented through roof. No more smells. Funnily enough it had been previously vented (some pipe through in loft just above AAAV) and previous owners thought best to get rid of. I don't understand how 3 plumbers missed it. diynot didn't though! Cheers

 

[Nige F]

I don't understand how 3 plumbers missed it.

That`s because they were gas fitters