What would cause the smell of sewer gas to come from a sink drain? The problem is in the 2nd floor master bath. The smell seems to come from the drain when I first turn on the water, and goes away after the water runs for a few minutes. I do not notice this smell in any other drain, and it only occurs when the water is first turned on, and not constantly. There is a trap under the sink. Any suggestions?

I wrote back in Sep about flushing my toilet and how it would fill up to the top of the bottom of the rim and then taking about an hour to go back down. You suggested having a company come out and snake the drain which I did. Apparently, it worked. They said they couldn't guarantee the work because there were "rug fibers" in the drain. I have just replaced my toilet w/ a low boy and it seems to have a hard time flushing anything completely. Do I need to have it snaked again? When it was snaked in Sep, they didn't see anything in the drain pipe so they did it from the roof. What do I need to do to clear up this problem permanently? Thanks for your help.