Sewer or septic gases and odors traced to building drain or vent piping defects:
Tthis article describes how to diagnose, find, and cure odors in buildings caused by leaks or other defects in the building drains or sewer line - leaks that make sewage smells or sewer gas smells or "gas odors" in buildings with a focus on homes with a private onsite septic tank but including tips for owners whose home is connected to a sewer system as well.
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Watch out: Because sewer gas contains methane gas (CH4) there is a risk of an explosion hazard or even fatal asphyxiation. Sewer gases also probably contain hydrogen sulfide gas (H2S) In addition some writers opine that there are possible health hazards from sewer gas exposure, such as a bacterial infection of the sinuses (which can occur due to any sinus irritation).
At left is a sewer line leak in a building crawl area.
[Click to enlarge any image]
In the page top photograph our client is pointing out an open sewer line in the basement of a home she was purchasing. The cap had been left off of a cleanout port where main waste line exited the building.
We suspected more trouble than just an open drain cleanout permitting sewer gases to leak into the basement.
Because this "work" appeared to have just been performed, right before our property inspection, we wondered if someone had been asked to attempt to clear a blocked connection between the building sewer line and the community sewer (or private septic system).
See Building drain odor source for more details about odors coming from plumbing drains - clues that may be more likely to appear in cool or cold weather. Also see our broad-scope article on diagnosis and cure of sewer gas and septic odors: SEWER GAS ODORS diagnosing, finding, and curing septic tank and sewer line smells.
Also see ODORS GASES SMELLS, DIAGNOSIS & CURE for procedures to diagnose and cure all kinds of odors in and around buildings.
What makes the smell in sewer gas? Sewer gases are more than an obnoxious odor. They are also explosive and they may carry bacterial or pathogenic hazards too. Depending on the sewer gas source and other factors such as humidity and building and weather conditions, mold spores may also be present in sewer gases.
We discuss plumbing vents as sources of sewer gas odors separately at PLUMBING VENT DEFECTS & NOISES.
We discuss plumbing fixtures, such as loose toilets, as sources of sewer gas odors separately
at PLUMBING FIXTURE TRAPS.
Plumbing drains and traps may smell regardless, as they are usually a reservoir for organic debris.
Remember that a building drain can be leaking inside of a wall or ceiling cavity without showing up as a wet spot or mold.
But if you notice a sewer gas smell particularly at one or more plumbing drains, the fixture may not be properly vented.
If the plumbing fixture or drain "gurgles" or makes funny noises when it is draining, or if you hear gurgling noises at some fixtures, say a sink or tub when nearby fixtures are draining, we would certainly suspect that the fixture is not well vented or may not be vented at all.
If you suspect that odors are due to a problem with the building drains but you cannot find a drain line leak nor an open drain cleanout cover, take a look
at CLOGGED DRAIN DIAGNOSIS & REPAIR.
The sewer gas odor may be coming not from a wet building drain (discussed just above) but from the dry or vent portion of a building's drain-waste-vent system.
CHINESE DRYWALL HAZARDS discusses Chinese drywall odors, sulphur smells, and corrosive outgassing hazards in buildings. Major costs to remove this product, repair or replace electrical wiring, plumbing, and HVAC components may be involved, and there may be immediate safety hazards due to damaged smoke detectors or carbon monoxide detectors in buildings where Chinese drywall outgassing has caused damage.
But on occasion we trace a sewer or septic gas odor to a hidden leak in a drain or vent line passing through building walls or ceilings.
At left our photo illustrates how hidden vent piping leaks may be lurking in an old building, a new building, or in one that has been renovated.
When the installer needed to extend the plumbing vent and drain line to an upper floor of this 1920's home, s/he simply broke open a cast iron vent pipe that was in a lower floor bathroom. There the "plumber" jammed a plastic ABS drain line into the open cast iron waste or vent pipe.
Our pen points out that this connection was certainly not sealed, and that sewer gases or septic gases were readily passing up the vent and/or drain line, into the building walls, and into the occupied spaces.
Continue reading at PLUMBING VENT DEFECTS & NOISES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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(Dec 12, 2012) Anonymous said:
I would like to read about sewer gas smell in hi-rise, tall buildings.
How building stack effect may influence the sanitary venting system
How tall stacks may affect the venting system
(Mar 25, 2013) Overwhelming Pond smell in kitch said:
This pond-like smell has been with us for a few years. When it's there, dishes have to be rewashed in dishwasher. Sink stinks.
Here are all of the steps we've taken, to no avail:
replaced J trap, snaked main, replaced disposal, replaced dishwasher, replaced airgap, installed Culligan water treatment, cleared roof vents, dug under foundation (found no sump/standing water). Have 5 yr old MicroSeptic septic system that has checked out ok. Smell does not smell like septic. This smell has baffled 3 plumbers. Not sure what to do now. It can be overwhelming and then gone the next day. Reminds me of a stagnant turtle pond. Any advice welcome. Thanks!
Forgot to mention, J trap is working..always has water when checked
It sounds as if you have sewer gas backing up your drain-waste-vent system, right? But you don't say just where you observe the smell. Is it from a single drain or all drains, or from elsewhere in the home?
With more details I can offer more specific suggestions like looking for a leaky drain or vent line (perhaps using a pressure test), inadequate venting, or even needing a trap or check valve on the main waste line.
(Jan 8, 2015) Garrett Boone said:
Hi, I moved in to a house last January and ever since there has been a horrible smell that comes from the outside everytime the water is ran, especially when it is cooler outside. I have had two septic inspectors come out to check the tank and leach lines and they both varified them working properly. One inspector suggested having the pipes in the house hydrojetted and the other recommeded placing risers on the septic tank.
The house was built in 2005 so I am guessing it is not a design flaw, rather something has broken or become clogged. Nobody could live in the house, with it smelling as bad as it does outside. I also called a plumber and he said the house needs to have a smoke test done to inspect for leaks but this is going to cost 400 in addition to the 400 already spent on the inspectors. I need some help diagnosing the issue rather than spending all this money on specualtions. Thanks in advance for any help!
I'm not an enthusiast of spending money on repairs before we know what needs repairing. That approach sometimes makes sense if the repairs we try are easy and inexpensive, otherwise probably not.
I don't assume there is no design flaw or even more likely there may be an installation flaw such as pipe settlement in trenches, broken lines, etc.
If we think this is a wet drain problem then see if you can find a plumbing company who have a drain inspection camera that can be run through various lines to look for the trouble.
If the problem is a plumbing vent problem I'd think you could track that down by when and where the odors occur - e.g. downdrafting from a roof?
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