Toilets, Sinks, Showers, Tubs and Disposals - Bathroom Odor

About a week ago the bathroom in the hall became filled with a bad oder--like a sewer oder. We noticed that the toilet seemed to be leaking around the base. I pulled the toilet up, figering I needed to replace the wax seal. When I pulled the toilet up, nothing seemed out of the ordinary--the old wax wing did not appear to be bad and nothing on the bottom of the toilet seemed unusual. We cleaned off the old seal, put the new one on, and reset the toilet. No leakes. When I got up this morning, the strong oder is back. Not sure what to do next! Any thoughts?

If the old wax seal had black on the wax, it was leaking. Next thing to check is the water level in the bowl. After it has set a while (overnight), mark the water level in the bowl with a pencil (so the mark can be easily removed later) and then flush the toilet. See if the water level is above the mark you made. If so, it is a vent problem. When other fixtures are used, it sucks the water out of the bowl so the trap is not doing what it supposed to (form a seal). You will need to go onto the roof (if safe) and check the vent pipe. Remove anything you can by hand and then flush with a garden hose.
Good luck.

What type of vent would I be looking for on the roof? Is it easy to find? I have the same problem and it is driving me crazy!!!