: We live in a brand new development on the top floor. Our bathroom smells most unpleasant - almost like stagnant water or sewage. There is an extractor fan in there, and it almost seems to be that the smell is coming from there. We have had a plumber out, but to no avail. It gets worse when it rains and sometimes the smell leaks into the other vents in the flat, ie kitchen and ensuite (both of which seem top run on the same line) Does anyone have any idea as to what could be causing it and how to fix it?

I too have been experiencing a dreadful drains smell coming from my en-suite bathroom and seeping into my bedroom.
It started after I had the bathroom roof extended downwards and outwards to create a passage space at ground floor level.
It is intermittent and is not connected with heat or rain, summer or winter - but it's truly dreadful.
We can not pin it down to any one unit - there is a whirlpool bath, shower, toilet, bidet and hand basin - but all units have a u-bend which you'd think would stop any smells getting up from the drains.
I think we need expert help to get to the bottom of this but don't know whether it's a plumber or builder that's needed.
I'd be most grateful for any advice.