air admittance valve

[mrcrow]

in my upstairs bathroom the wc is connected to a vertical stack which is inside the property but boxed in (the stack does not vent to the outside of the house) the wc connects to this by a bend which has a vertical stub into which is fitted a small air admittance valve (1 1/2"), which has a horizontal slot through it and has what seems to be a clicking valve inside when you shake it
i put a lighted candle beside the valve and flushed the wc, during the process of the water running down the stack there was no movement in the candle flame.
when the cistern was empty and starting to fill the flame then was sucked towards the air admittance slot
is this normal

when flushing the toilet the bath outlet gurgles and eventually i think the trap empties as i can smell faint sewage odours coming out of the overflow part of the bath plumbing and the waste hole

i suspect the bath is plumbed into the stack and it is sucking the water from the trap when flushing the toilet. i thought the air admittance valve would have catered for this, in any event.

the property was built in 2006

any advice greatfully received

cheers
geoff

 

[Nige F]

The 4" vertcal stack should have a 4" AAV on it - the 1.1/2 " one may have been added because the stack wasn`t functoning - it`s not adequate ,Now you could hire a borescope ( for about £15 ) and look inside the boxing via a small hole before you cut right into it and get @ the top of the stack to replace/fit a new AAV - or just go for it

 

[mrcrow]

The 4" vertcal stack should have a 4" AAV on it - the 1.1/2 " one may have been added because the stack wasn`t functoning - it`s not adequate ,Now you could hire a borescope ( for about £15 ) and look inside the boxing via a small hole before you cut right into it and get @ the top of the stack to replace/fit a new AAV - or just go for it

thanks Nigel
the stack finishes on its upper end with a 90* bend to take the toiled pan
on the top of this bend is a vertical stub of 1 1/2" and it is into this stub the mini aav fits via a black tapered washer and a blue washer and a screwed ring..
so because of that i cant follow too well the instructions you have given
can you let me know if i have understood you well enough.

cheers
geoff