We had our bathroom done in March this year, have had problems with a lingering/sewagee bad smell very occasionally but it has always gone away within the day and we assumed it was maybe just typical toilet bad smells but recently it has gotten worse and more constant so I have been trying to find the sorce with no luck.
Pretty sure its not a leak as im in a upper flat and would have heard about it, also no moisture to be found. So im assuming it might be a dodgy set up? and gas might be getting back in through a waste outlet?
I don't think its the toilet as it always full of water and I am convinced the smell is coming from under the bath somewhere. There does seem to be water in both the bath u bend and in the sink trap so im a bit confused as to where the smell is getting in?
The following pics show the setup, there pretty self explanatory I think but I can describe it more if needed, any advice would be greatly appreciated:
