Complex Sewer Gas Issue
Could you have a leak in a drain pipe under the floor and after the trap? It could be in a location that does not get the downstairs ceiling all wet but does let sewer gas escape.
If you put some bleach (two ounces should be enough) down the affected drain and let it sit overnight, would the smell go away in a day or two? (A "drum trap", common for bathtubs in homes built before about 1960, may need 4 ounces.)
Decaying matter may have collected in the trap for that drain, generating the sewer gas right there.
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.
Last edited by AllanJ; 04-29-2012 at 08:05 AM.