en suite odour

[Laburnum]

Our ensuite has a wc, hand basin and shower.

Ive checked and double checked the traps on numerous occasions, and they always have water in them.

There is no apparent leaks & the soil pipe runs internally.

Is there any suggestions or advice on where this drainy smell is coming from?

Many thanks in advance...

 

[Bahco]

Is the stack vented to outside

 

[Laburnum]

the stack is vented internally

air admitance valve is under the en suite, i know this because i hacked the ceiling off under to see if there as a leak...

do you think it may be too low?

 

[Bahco]

Air admitance valve is under the en suite,

Its supposed to be higher than the highest appliance its serving and sounds like it is stuck open too