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Question DetailsAsked on 2/24/2017

Sewer smell in bathroom

Had my toilet snaked as it was intermittently clogging. Immediately after the toilet was snaked, the bathroom began to smell of sewer gas (smells like curry). The plumber came back and said the toilet seal needed to replaced. It has been better since the seal was replaced (had it replace twice just to be sure) but the smell is still there (worse at certain times than idea why). Plumber came back and cleared the sink overflow drain and saw no leaks in pipes in the crawl space under the bathroom, but the smell is still there. Any thoughts on next steps?

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3 Answers


Smell can be worse at some times than other due to variations in humidity and airflow as building temps and outside wind/door/window opening/closing changes over the course of the day and from day to day. Also can be related to whether heat/AC is on - more so with forced air type of course, but also occurs with radiant/baseboard/radiator heating due to temperaature changes and convective airflow in rooms when they are heating.

Or if due to a leaking sewer pipe or toilet, then when the contaminated area around the leak gets wet from water running/flushed again, smell would get stronger again.

Possible sources of the smell in no particular order - start with easiest ones for you to try and work up from there as needed:

1) Could be the clog (either when formed or when snaked out) blocked the vent pipe to the roof, so the sewer gases cannot vent - hence they come up through the traps in the fixtures. Snaking, or sometimes (depending on how vent piping is run) just running a hose into the top of the vent pipe opening on the roof (with someone keeping an eye open inside the house to be sure the water is not backing up somewhere because of a clog in the drain lines) will clear it. If each fixture has individual vent connection to the trap exit area, hose through roof will commonly NOT solve it because the water will run right down the main vent pipe to the sewer line at ground level, not through the individual branches to each fixture.

2) If it is real cold where you are, check the vent pipe did not coincidentally choose this time to frost up at the exit point above the roof - and is not blocked by deep snow buildup on the roof.

3) Since you say it got better after the wax seal replacement, leads me to wonder if your toilet is sitting on top of thick flooring (rather than the flooring stopping at the edge of the toilet) - which is fine, but requires a thick flooring wax seal (which is almost twice as thick as a regular one) to seal correctly.

4) Run a bunch of full hot faucet water with some liquid dish soap in it (lemon scented like Mr Clean if you have any) through any other drains in the room - shower/tub and sink presumably, and floor drain if there is one. Could be there was a backup into them too, which got past the trap into the exit part of the fixture and is stinking.

5) Could be snaking broke a weak or corroded pipe, or caused a joint to come loose so it is leaking a bit

6) If the toilet was clogging and backing up from inside the pipe (rather than inside the toilet as is usual) and the wax seal was leaking, could be you have sewage in the subfloor and/or under the flooring which is stinking, even if the wax seal is now OK. Unless there is a lot or is still getting wet, will stop smelling after a week or so, though can start smelling intermittently again during high humidity conditions.

7) could be the flange or its threads ares broken/corroded, so while the wax seal is sealing to it and the toilet, the flange itself is leaking

8) rarely - wipe down with toilet paper to check for wetness and inspect closely (use mirror to see back side) a cracked toilet will let gases out without leaking any or much. Cracks usually occur on the casting mark down the centerline of the toilet front and back. Also wipe around base of toilet for any dampness coming out from under it (if not fully caulked).

About only way to tell if the wax seal is leaking is removing the toilet yet again and checking for wetness around the flange hole area, and down along the drain line below the flange. To check if subfloor is wet normally you need to open a hole in underlying ceiling (sometimes can get in around a light fixture) - best with fiber optic inspection tool/camera (rent for $15-20/day typically for flexible inspection scope, or more like $30-40 for a fiber optic camera scope - or buy at Amazon or Harbor Freight for about twice that). Fiber optic inspection scopes/camera only need about a 1/2" hole to go through, so a lot less destructive to underlying ceiling than cutting a foot square hole for eyeball inspection. And if you are lucky with light placement relative to the toilet, might be able to sneak in alongside a light fixture box after removing the fixture (obviously turn power off to that fixture when doing this) and have the access hole partly or totally covered over by the light fixture base plate.

Another way to track its source - realizing sewer gases are generally explosive so be careful about smoking or turning switches or fans on or off when removing the covering until the gas has had a chance to dissipate - you can tape over sink and shower/tub drains to block them off, and use extra large plastic contractor size garbage bag, dry cleaners dress bag, or plastic sheeting with tape around the toilet for say overnight to see if blocking off a source area stops the smell. And of course smell when removing the cover to see if trapped gas excapes at that time.

One other thing - if smells like curry rather than urine or sewer gases, makes me wonder if maybe the cause is not a leak (from sewer pipes or wax seal/toilet) constantly rewetting a wet area in the subfloor or flooring which si starting to develop fungal growth - a form of wood decay where fungal growth which can look like toadstools or yard fungal growth starts growing on the wood, and will go dormant when it dries out, then start stinking again when it gets wetted and regrows. Has been described as fatty rancid food, garbage can smell, dead animal smell, cloying wet woody smell, etc - so I guess curry smell might fall in that range. Unless you have a neighbor (in same building) who uses a lot of curry I certainly would not expect sewer leakage or gases to be described as curry-like.

You can also find a fair number of other previous similar questions with answers concerning bathroom odors in the Home > Plumbing link under Browse Projects, at lower left.

IF you need professional help with this, I would say maybe a different plumber since the one you have seems to be at the end of his thoughts on why this is happening - though of course that means you would be paying for it. Though except if the wrong wax seal was used, unlikely to get any more effort out of the original plumber without paying either - because he will likely place the blame on existing pipe issues - cracked pipe, bad joint, corroded pipes, etc. Or on leakage at the wax seal when the toilet was clogging, so before his presence on the job.

Answered 3 years ago by LCD


oops - did not catch onto the crawlspace thing - if he did not see leaks or smell it down there, then could be a vent issue, could be backup into the traps in sink or tub (flush as I indicated - you can also run some vinegar and baking soda through to eliminate the smell but flush out after a couple of minutes sit time to prevent excessive corrosion from the vinegar.

Or could be excessive leakage in seal area wetted the subflooring enough that it is rotting - though that will stop if the moisture source goes away.

Here are a few links to similar questions - others below them and in the Home > Plumbing link in Browse Projects as mentioned before -

Answered 3 years ago by LCD



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Answered 3 years ago by Member Services

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