I've just registered in order to post on this thread which I found after searching for causes of a sewage smell in the bathroom. I've had various traps and pipes replaced, drains and soil stack checked, water board and council checking their drains, all to no avail.
Like for most people here, the stench is awful on a sunny breezy day with the window open, and only when the wind is blowing into the room. The wind has been from the wrong direction a lot of the time, or it's been cloudy, so the various tradesman haven't smelt it at all!
I had discounted the paint theory even though I'd heard of the problem, because there was a fustiness in the bathroom well before the painting was done, in fact I assumed that new flooring and paint would freshen the place up. Water had got in some months before from a problem with the roof and the painter found a patch of mould when he stripped off the paper. He cleaned it off and sealed it, papered with lining paper and painted with Johnstone's bathroom paint.
Now I'm wondering if the original fusty smell was caused by the mould, and somehow the paint has made it much much worse, though I haven't seen Johnstone's paint mentioned as a problem. I'm going to get it redone with the Zinsser as recommended here, and I hope there are still people around who can tell me if it did the trick long-term before I spend yet more money! At least in my case it's only one room, but you'll understand that I'm at my wits' end.
