Q. We have an odor problem in our bathroom. It comes from somewhere in or around the toilet and is not a rotten or sewerage smell but most unpleasant. It doesn't fill the room but if you are near the toilet you can smell it. It is not a constant odor but is noticed fairly often and more frequently lately. Since we first noticed the smell we have replaced the toilet because the old one was cracked. We still have the odor. My husband says he is sure the toilet is sealed properly. We only have this problem with the second floor toilet and have never noticed the smell from the first floor toilet. Our home has a septic system and I can't help thinking the odor is somehow coming from the septic system. Is that possible? What else could cause it and can it be fixed?

A. The hardest part of your problem is the most important piece of the puzzle and that's locating the source of the smell. Let's run down the list to see where to even start pinning this one down. It's only in the one bathroom so that lets the water sup ply off the hook. It's not stinky water. You say you had the problem prior to installing this toilet so that lifts some of the suspicion off the new toilet but not entirely.

You might remember a lady some time ago with a similar problem who wrote to me and together we hit our heads against the wall trying to figure out just where the smell she had was coming from. I had her check everything. I told her to clean out everyth ing from the under sink cabinet where sometimes a wet or damp rag or sponge will get stowed and start to smell. No matter what she did she couldn't get rid of that smell. Then one day she was going through the medicine cabinet when she opened an expired bottle of liquid gel vitamin supplement tablets her athlete son stuck in the cabinet long ago. The moment she open the bottle she almost lost her footing the smell was so bad-- she'd found it. Try checking anything stored nearby that could be contribut ing to the problem. If you've ruled everything you can put hands on out, including lifting and reseating the toilet itself-- that's not a hard job and if your still fighting the problem it's just one more thing to double check--then the next suspect is the plumbing venting itself. I had a situation with a house that every time the fireplace was burned the kitchen stunk like septic. I even traced it with a gas detector. The lady of the house wouldn't allow a hole to be cut in the dining room wall to investigate the pipes but ultimately the kitchen was remodeled and the kitchen wall was opened and an unsealed stub in the waste line for a future fixture turned out to be the culprit. When the fireplace burned it drew air from inside the house and the open stub acted like a septic vent inside the wall. A variation of that may be happening in your bathroom. You could have an open or slipped joint in the plumbing vent pipe in the wall. It won't leak water because there is no plumbing drain higher up the vent so it'll only pass air. And you smell it.

There is a process called a smoke test that might reveal the presence of a problem with a vent pipe. Old-time experienced plumbers know how to do it. You pop the top off of the septic tank inspection port-- that white plastic or cast iron thing over the septic tank in the yard. Then as a pre-test I always ask that a toilet be flushed so I can listen for the water to enter the septic tank telling me that things are running as they should. Smoke is introduced down the vent stack from the roof. After a while you'll see some smoke come out of the pipe in the yard. If any smoke appears in the house then that's where the problem is and the wall can be opened, the problem identified and fixed. The means of introducing smoke that I have seen included ever ything from smoke candles propelled by hair dryers to wet rags and a beekeeper's smoker to get the job done. A more modern method would involve a remote TV drain inspection introduced from the roof and that's way high-tech but costs lots more than the ol d fashioned method. Good luck and wouldn't it be nice if you found something like the old vitamin pills to solve the problem the easy way.