Sewer smell in basement - why??

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Posted by: from Thorold
11/12/2012 at 10:56:03 AM

We did a bathroom update approx 8 years ago, where the plumber changed the toliet line to main out line... recently we have had a sewer smell that overtakes the basement. (What can we do ? And is the bad smell toxic?)

Also noticed in front yard (summer) that all the grass died due to lack of water - except- where the water out line would run - would this be why?? there are no trees on front property..


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Date/Time11/12/2012 at 12:22:25 PM

Can't comment on the toilet line and grass issue, have my thoughts, but I can say that MOST sewer smells in the basement are the result of no water in floor drain.

To add to the fix on this I will also say that 3 Tbspns of VEGETABLE oil on top will help the water from evaporating. The vegetable oil is biodegradeable and will not promote a fowl smell like other oils.

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Date/Time11/12/2012 at 1:24:29 PM

Hello Karyn :

When the plumber installed the new toilet he likely has disturbed something else. The only time a sewer smell can get back into the house is through the traps as Stu in his comments says or a vent has a hole in it somewhere.

The only way you can tell that is have a plumber send up a smoke trace into the vent and see what happens. If you can detect it that way it would be an easy repair.

The only other way if the odor is in the basement is there is a leak outside in the main line and it is coming back into the house via the sump pit and your weepers and that would be also hard to detect.

Good luck.


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Date/Time11/12/2012 at 3:17:28 PM

Get a plumber in to scope the drain, until you do so every answer here is just guessing...the grass is green for a reason and more than likely is wet, broken pipe somewhere.

Karen these gases are toxic, get the pros in asap.

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Date/Time11/12/2012 at 6:20:16 PM

Hi Help,

That sewer smell is not a good thing. It means methane gas is leaking into your house. This could be a venting issue or a proper sewer back up stop valve was not installed. Either case, it means that there needs to be a serious investigation.

I don't believe your lawn issue is connected.


Dunn-Right Contracting

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Date/Time11/13/2012 at 7:27:20 AM

First the smell is toxic and flamable and should be fixed ASAP. Unless your sewer line goes out to the street close to the surface, say 2-3 feet down. Then the green grass is not related. Water usually travels down from a leak and grass roots are only 3-4" deep, so the grass won't benifit from a sewer leak.

If you live in the country without city services then you have a septic system and the green grass would be normal as the tank and field lines are only 1-2 feet deep.

With a septic sytem you will have a sewage pump in the basement to connect to the septic tank. If that is not working or the cover is loose, you will have a smell, check that first.

Unless you can see all the piping in the basement, it would be best to get a plumber in who has a snake with camera to look at the drain lines, and a smoke machine, so the vent lines can be checked.

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Kerry from KCO Holdings Ltd. in Calgary
Date/Time11/13/2012 at 11:16:35 AM

Every plumbing fixture in a home, should have two items working together to keep sewer gas out: (1) a p-trap that holds water in a "U" shape of the pipe and forms a seal, and (2) a vent system that allows air in to equalize pressure and lets sewer gases escape up the stack to the outside. In short, the properly-vented p-trap prevents back pressure from letting sewer gas into the house. The vent is a critical component of this system because the pressure in sewer lines may fluctuate.

If the fixtures had remained unused for a long time, it very likely had a "dry trap." There are several suggested remedies. Each of them use ordinary household products, such as baking soda, white vinegar, table salt, baking powder, hydrogen peroxide, chlorine bleach, boiling water. NEVER mix vinegar and chlorine bleach. Mixing bleach and vinegar releases chlorine gas. This yellowish gas is harmful if inhaled, as well as irritating to your eyes, nose, and throat.

If the odor had persisted after the vinegar-baking soda or bleach-hot water-mineral oil technique, the sewer gas invasion might have been caused by something other than a dry p-trap. Leaks, rotted or cracked drain pipes, clogs in the drain or a stopped-up vent pipe are other potential "stink" makers. If you still smell that nasty odor when you open the bathroom door next morning, stronger measures are in order. It is been time to call in the professional a licensed, bonded and insured plumber.


Kerry Oberg

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