About two years ago, I had my 2nd story bathroom remodeled. For months, it
was completely fine, but recently, there's a bad smell from the bathroom
sink. It drains well .. But to get rid of the smell, I did try a draino
type liquid. Didn't fix the problem. This has been going on for months
now.

It smells like rotten eggs .. maybe sewer gas. As I said, the plubming
under the sink is updated, up to code, and has a trap there, which would
make me think it's not sewer gas. -- I've opened up the trap there, and
it's clean as a whistle.

Also, generally, you smell it more when the water is on.

Could it be something like my vent pipe to the roof is clogged, forcing gas
through the trap? -- No other drain in the house has this problem, btw.

Any ideas? Thanks in advance.