Can't figure out where smell is coming from in bathroom

[Mattdub1]

Hi,

We moved into our house in June last year. For the past few months I have noticed a stale smell that is possibly sewer gas in our basement bathroom. It is FAR more noticeable with the exhaust fan on and door closed. I have sniffed every fixture in the bathroom and cannot identify where it's coming from. My upstairs bath is located directly above, and there's a hole in the subfloor for some of the jacuzzi piping. I have tried to investigate from above but I don't smell anything in the space above the bathroom. I also have used my phone light/camera and don't see anything out of the norm above the bathroom. . My wife was convinced it was the exhaust fan, so I replaced it and ensured the piping was secure. It vents out the side of the house. Didn't get any better. I thought it was the older toilet in there, because my thought was negative pressure from the fan could be pulling gas out a leaky seal, so replaced the toilet and it seemed to get slightly better for a few days.. I thought things would continue to improve and haven't noticed as strong of a smell for a week. I showered yesterday in there (shower is used daily), and left the fan on. Came back in few minutes later and the smell is back, although not as "hit you in the face" strong as before.

Surprisingly, when I had the toilet off, I didn't smell anything coming out of the sewer pipe on the floor even after 30 min of not being plugged with a rag. When I replaced the upstairs toilet after we moved in, there was quite a strong smell the entire time I worked on it...So I don't know if what I'm smelling is even sewer gas, but I don't know what else it would be.

I cannot for the life of me figure out what's causing this. The toilet seemed to seal nicely and I have replaced several before, so not my first time. Stuck my nose in the shower drain and didn't smell much there either. Same with sink drain and I sniffed all around base of toilet.

Any thoughts/suggestions would be very much appreciated!!!

 

[Cwhyu2]

Did you check if you have any floor drains, they may have lost their trap seal.If so pour some water in the floor drains.

 

[Sponsor]

 

[Reach4]

If you can tape (with good removable masking tape) a thin plastic drop cloth that isolates the toilet, and the floor around the toilet, you can see which side of the plastic the smell occurs on.

You could use weight to seal the plastic to the floor, rather than tape.

 

[Mattdub1]

Update...I have had the door shut and fan running this morning for two hours and no smell. I just ran the shower to steam it up a bit in there and no smell. It happens at very random times. Yesterday it started at about 2pm and went on for several hours.

Regarding the floor drain, I only have the tub drain down here on this whole side of the house. I can't actually see the trap because it's under the slab. I have an access panel behind the tub, but it's a fiberglass tub/shower so I can't see the trap. It goes down into a hole in the slab. There should be one though as the basement was finished in 2001 and there are a bunch of permits here for all the work. The only other drain is near the furnace on the opposite end of the house, which is a floor drain and there is water in it...

 

[Plumber69]

This happens at my house sometimes when the window is open. The vent is to close to my window

 

[Mattdub1]

I believe my vent goes through the roof and I have no window near this bathroom

 

[Mattdub1]

More details - per a forum members suggestion, I ran a load of laundry upstairs and nothing changed. Still no smell this morning. What is weird is that I have been running the fan on and off for the last week to make sure the new toilet fixed the issue and I never really smelled it again until yesterday. Is it possible that it's a slow leak from somewhere and the sewer gas gets worse smelling at certain times of day? Is it odd that when I replaced the toilet, I didn't smell anything at all coming out of the open sewer pipe? Or does sewer gas not smell all the time?

 

[Reach4]

Also try correlating with the wind. You may be able to get wind history for an airport near you.

Here is an example: http://w1.weather.gov/data/obhistory/KRFD.html See the Wind column for direction and speed.

 

[Mattdub1]

Are there any other troubleshooting steps I can take?
Would a plumber be able to test that the smell is indeed sewer gas? I saw a few gas testers at home depot that say they test for methane, but not sure if they work well for sewer gas detection?

 

[Anthony Curtas]

We had something similar in our master bathroom (currently being redone). It was coming from the shower which was losing its trap seal. When I tore up the floor I found that the shower had a 3/4 S trap and shared a vent with the toilet (they joined together before the stack). So it was likely the shower either siphoned its own trap or the slug of the toilet "rocked" the water in the trap as it went by and eventually went below the seal line (weir) or just plain siphoned it.

Not sure how you'd confirm that. I didn't solve the mystery until demo started and I saw the whole DWV system.

 

[FullySprinklered]

Does your basement group drain by gravity, or is it pumped?

 

[Cacher_Chick]

You should be able to look down the sink and shower drains with a light and SEE if the traps are full of water or not.

 

[Mattdub1]

Does your basement group drain by gravity, or is it pumped?

I'm not sure what you mean by pumped, but we are on city sewer. I don't have any pumps in the sewer system in my house.

 

[Mattdub1]

You should be able to look down the sink and shower drains with a light and SEE if the traps are full of water or not.

I will check but right now this is one of two main bathrooms...And it is the main shower...the shower gets used twice a day most days, sometimes 3 times. The sink is used frequently throughout the day as well, so I wouldn't think it would be caused by a dry trap, but I could be wrong.

How long would it take for a trap to siphon out, if that were the cause

 

[Jadnashua]

IF a trap is not vented properly, it could be siphoned in minutes.

Double-check the toilet to see if it can rock at all. IF it can rock, and you used a wax seal, it is no longer sealed! If the toilet can rock at all, you need to pull it, dry fit it with shims to ensure it will sit stable, then add a new wax ring and anchor it down.

In most places, code calls for sealing around the base of the toilet to do two things: help hold it in place, and to prevent crud from accumulating underneath the toilet. You don't want to use an all silicon caulk, as that will make removing the toilet a pain. Code generally requires you to leave the rear of the toilet unsealed.

Is the shower a tub/shower, or a plain shower only? Does it have a tiled shower floor? One study said that 70-80% of tiled showers are not installed properly. One common mistake is to put the liner flat on the floor which violates the plumbing code. If it is flat on the floor, the moisture that gets under can't properly drain, and it can start to smell like a swamp.

 

[Mattdub1]

IF a trap is not vented properly, it could be siphoned in minutes.

Double-check the toilet to see if it can rock at all. IF it can rock, and you used a wax seal, it is no longer sealed! If the toilet can rock at all......

Toilet seems rock solid. I dry fit it with shims which took awhile because the tile had some lippage under the toilet in several directions. I had to use several shims around the base, and was very anal retentive about getting it to a point of no rocking whatsoever. I then pulled it up, set the wax on the flange (standard wax, no horn), then lowered the toilet. I then pushed the toilet down and it felt like I got a good seal. Since it's hard to set the toilet in the EXACT spot where I dry fit it with the shims, I then very slightly adjusted the shims, since the slightest amount of movement did make a difference. I never lifted up on the toilet during that process, and then tightened the bolts once the shims were satisfactory.

The shower is a one piece fiberglass surround

If it were a siphoning trap, wouldn't the smell be a little more consistent?

Also, is it normal that when I pulled the toilet, I didn't smell sewer gas at all? Could it have just been that time of day when the sewer line didn't stink? I just find that odd because I've always smelled sewer gas other times I pulled toilets.

I can pull and try resetting the toilet again if you think that's necessary, but wanted to try ruling out other options first since the shimming process takes so long to get it perfect with my tile situation.

Thanks

 

[Cacher_Chick]

The smell that comes up can vary in amount depending on the configuration of the piping and the forces that are in the line to push the air back up into the space. I have pulled toilets where the wind could be felt (and smelled) pushing air back up the line, where more often than not the amount of air movement is negligible.

 

[Reach4]

Is isolating fixtures with thin plastic not practical for you? Sniff which side of the barrier has the smell.

 

[Mattdub1]

I will be trying that today, Reach4. My concerns are that the back of the toilet will be hard to do that with because there's only about 3/4 inch between it and the wall. The other issue is it's so intermittent, that I don't know when to lift and check the plastic. I have not smelled it in two days now.... But will definitely give it a try.

I also looked down the sink drain and see water there. When the toilet is flushed, the water moves down and up in the trap, but doesn't appear to suck the trap dry. I assume this means the sink and toilet share a vent?

 

[MattCT]

Wow, I'm going through something quite similar. Today I had a plumber poke holes in the walls to see if we could determine the source, which appears to be from the main drain/vent stack from the basement to the roof. Our issue is in the upstairs bathroom but we do have a faint smell down in the basement through some electric fixtures. The smell is worse after showering or using water. We are on septic.

We've checked all the traps and the wax-ring of the toilet. Cleared the roof vent (which was clogged) and ran water through it all the way down. Oddly enough, no signs of water anywhere so plumber believes the issue is above the toilet connection to drain/vent. Tried a peppermint oil test and that lead us to the attic and plumber added some silicon to the seals of the cast iron drain pipe/vent.

At this point I want to limit the amount of holes in the walls until we can better determine where the leak/crack is coming from. Finally was able to secure smoke-test through a plumbing company. Was hard to track down. I do believe if this is done properly it should find the issue quickly.

Good luck! I know how frustrating this is...