Terrible smell from bathroom drain...
3 year old colonial. In the 1/2 bathroom downstairs, there's a fishy/sewery smell emanating from the bathroom sink drain. This bathroom is hardly used (maybe once a day, if that). We tried letting bleach sit in the trap (no effect), liquid plumr (in case something was in the trap (no effect) and running the water for several minutes. I'm suspecting that sewer gases are emanating back up the chain and out the drain.
I would think that standing water in the trap would "seal" the air flow, but this doesn't seem to be happening. This is the first time we've noticed this. I'd rather not take the trap out to investigate, but if I do, what about putting on a deeper trap to ensure that more water sits down there, possibly blocking the gases from coming back up ?
Interestingly, we notice the smell is worse on windy days - I suspect that the wind is acting as suction over the roof vent and drawing the gases up even more.
Thanks for any insights/solutions.