I don't know if there are any plumbers here or not, but maybe someone can chime in.

One of my bathrooms smells like a sewer pipe. The other two don't.

I replaced the wax seal under the toilet a few weeks ago and it seemed to help for a while, but now it's back full-force.

What could the problem be? I don't think I installed the wax ring that badly (what is there to screw up?), but I'm not going to totally discount it. But if there's some other reason this might be happening, I'd like to know.

I know if (and, probably, when) I call a plumber, he's going to come out and just replace the wax ring, despite the fact that I will have told him that I've already done it. So I'd like to avoid that if possible.