We are capable DIYers who did a remodel on our hall bath this summer. While that one was under construction, we have been using the tiny master bath. However, there has been a sewer smell coming and going from the master bath almost the whole time we've been under construction. What I really would like to know is how to test or narrow down the possible causes to find the problem to fix, especially if it's not going to be something we can fix ourselves.

The master bath was mostly unused before we started our construction, so there is a possibility that it smelled before we started construction & we never noticed it. We began using the master bath daily after the demo on the hall bath started. The toilet in the master was replaced prior to construction start because of how cheap it was & how poorly it flushed. I'd say the smell started after the demo was finished & before we finished the plumbing work. I tracked it down to the space between the toilet & the wall to the left. The toilet is on an outside wall & I know there is a vent stack going up to the attic in that outside wall. We thought for a little while it was maybe the wax flange on the toilet not being set properly & we had planned to redo it.

The smell stopped for a few weeks it seemed, and then started back up again only this time also in the sink area a few feet away - not in the cabinet under the sink but only above the sink. The sink shares a drain & vent stack with the washer & dryer, NOT with the toilet. We still are not using the other bathroom but there is no smell there.

The thing that's made this tough to diagnose - and I have searched online to see what I can find out - is that the smell comes and goes, isn't there every day & happens at different times of the day. I haven't gotten up into the attic when the smell is present to find out if it's also up there, but I will.

I could provide a drawing of how the plumbing goes if necessary to figure out the problem. I read "Tom & Marks Timely Tips" & I apologize in advance for posting about smell help! I have some theories about what it might be, I just hope I'm wrong!

Thanks for your answers!

Godly1962, the only reason I didn't think it was build-up is because that bathroom was remodeled less than 3 years ago by a pro plumber and never got much use until a few months ago when we started the remodel of the <i>other</i> bathroom. The smell started not too long after we began using the bathroom, but is intermittent; some days it's stronger than other days and some days (like today) it doesn't smell at all. I'm certainly willing to try the boiling water, I just don't know that it can all build up that fast. We never had the problem before in the old bathroom with 25 year old fixtures.

ma0641, we do think that it could be the wax ring & we have one ready to go. But it unfortunately doesn't explain the sudden sink smell. Unless it's possible to be so unlucky as to have a problem with the wax ring and then build-up in the sink!

Ok so I've had this same problem in my bathroom upstairs, and I've looked all over the internet for an answer so one answer said to boil hot water and pour it down the drain and sink in the bathroom, but 1st pour a gallon of bleach, well the smell was so bad and I was desperate that I just boiled the hot water, it worked GREAT! I'm going to do this about once every 2 weeks, I think too it's the build of hair and shampoo/and just hair products, you know a lot of cleaners and hair products contain wax and oil and when hair is mixed in well it is disaster. Also, these new fixtures in your bathroom have a safety feature on them in the bathtubs so that you don't get scalded during a bath or shower, but the sink is hot,hot,hot scalding hot, but not the bathtub because it's a safety measure. So therefore, that being said, that is why we need to pour boiling water off the stove to push the crud down the drain.

"Sewer" smells in bathrooms are usually associated with a bad wax ring. Stuff wet tissues around the base of the toilet and see if the smell stops. If it does, change the wax ring. If it doesn't, you could possibly have a disconnected or cracked vent pipe or fitting.

Maker sure you have water in the sink trap.