Sewage odor tracing procedures:

Tracing odors occurring in cold weather.

This article describes approaches to track down the actual sources of sewer gases in or around buildings when those are observed principally in cold or freezing weather.

How to Find & Fix Sources of Septic Odors that Occur in Cold Weather

Some of the diagnostic steps given here pertain to all seasons. But here we focus on cold-weather-related sewer and septic odors in or around buildings.

At left is a plumbing vent that was almost entirely blocked by frost.

[Click to enlarge any image]

Smelling sewage odors inside only, or mostly inside

Here are some places to look and perhaps to fix if you're smelling sewage or septic like odors inside of a building:

• All plumbing drains and traps 
  
  may smell and produce a little methane gas: Beware of mistaking normal drain odors, or gases detected with very sensitive instrumentation for an abnormal condition or a problem.
  
  A little gas odor is detectable at many fixture drains and traps since there is likely to be decaying organic matter there.
  
  Check for dry plumbing traps. If the trap is dry and odors are present, that's a problem and we'll need to determine why the trap was dry: from dis-use and evaporation, from siphonage, or some other fault such as a rusted through or leaky trap itself.
  
  See PLUMBING FIXTURE TRAPS and
  
  see BUILDING DRAIN ODOR SOURCES
• Blocked or Inadequate Plumbing Vents 
  
  can cause odor backdrafting into a building.
  
  See PLUMBING VENT DEFECTS & NOISESfor diagnostic details.
• Cold weather
  
  related to sewer gas odors -
  
  see COLD WEATHER & PLUMBING VENT BLOCKAGE PROBLEMS as a Source of Building Smells, Septic or Sewage Odors
• Dry Plumbing Traps
  
   can serve as a Sewer Gas Odor Source indoors - check all of your fixtures, especially ones which have not been used in some time or ones which are lacking proper venting. A plumbing trap serving an unused sink or shower or tub can dry out and permit sewer gases to enter the building up through the fixture.
  
  See TRAPS on DRAINS for diagnostic details.
• Plumbing Fixtures 
  
  which are not properly vented may lose their water trap: If the fixture is not properly vented, even if it's in-use, the water that is supposed to be in the fixture trap may be siphoned away, permitting sewer gases to enter the building.
  
  See Plumbing Vent Defects for diagnostic details. [A live link to this article is just below]
• Plumbing vents
  
   as an odor source: a leaky plumbing vent could be an odor source indoors. The odor may not be coming from plumbing drains: If none of the building drains are clogged or slow and if the septic system is otherwise working one's first guess would be a problem with the plumbing the vent system. This condition can occur year round.
  
  See PLUMBING VENT DEFECTS & NOISESfor diagnostic details.

You can usually spot inadequate or blocked plumbing venting

by noticing, for example, that tub, shower, or sink drain makes a gurgling or "glub glub" sound when a nearby toilet is flushed or when a full fixture is being drained. Inadequate or blocked plumbing venting can also mean that a plumbing fixture does not drain well (even though the drain line is not blocked). Inadequate venting produces a glub glub sound as water passes down a drain and cannot draw air in after itself through a plumbing vent stack.

Instead the drain has to draw air in to itself through various plumbing traps which, as they normally contain water, produces the glub glub sound as air passes through the trap. This defect can siphon water out of traps and let sewer gases back into a home - smelly and potentially dangerous (methane gas).

Also see PLUMBING DRAIN NOISE DIAGNOSIS: that may indicate defective or clogged plumbing: how to diagnose and cure drain sounds.

How to improve sewer or septic gas or methane gas smell source location by considering the effects of weather conditions or season. Causes and cures for sewer gas odors related to wet or cold weather. How to find and cure bad smells in buildings using site and outdoor conditions as diagnostic

Some of the diagnostic steps pertain to all seasons. The photograph provides a lot of septic odor diagnostic information if you look closely: there is a home made septic tank nearly touching the building wall (by those steps), and in the foreground is a pony pump that the owner was using to try to move septic effluent uphill to his drainfield.

This system would not work reliably: the tank is too small for normal use and the pump is exposed to freezing.

• Locate the outdoor private septic or public sewer line components -
  
  septic tank and fields, or their probable location. Melted areas of snow can be helpful as they often mark the location of even properly-working septic system components - the soil is warmer at the septic tank and at the drainfield lines.
  
  As in the two photographs of snow over septic fields (left) and over a septic tank (right), if you see snowmelt, the system is probably not frozen. Warm effluent is entering from the septic tank and bacterial action is progressing in the soils.
  
  If you do not see septic effluent coming to the surface of the yard and if drains are not backing up inside the outdoor parts of the septic system appear to be working.
  
  But how do we know if the septic system is frozen and not accepting waste from the building? What if we think the septic system is blocked by freezing?
  
  See SEPTIC INSPECTION & TESTING for details.
• Before doing anything costly
  
  it's important to do your best to properly diagnose the problem.
  
  Do NOT hire a company to "rejuvenate" your septic field nor to install or flush or use any other magic product. It would be a better investment to take the cash you'd have paid them and rip it into small pieces and flush it down the drain.
• Blocked plumbing vents?
  
  check for a plumbing vent that has become blocked by snow, ice, or even a dead animal
• Frozen septic fields:
  
  A septic system can become frozen in prolonged very cold weather if the system is also not in regular use.
  
  If the septic field froze and stopped accepting effluent, or if it were totally blocked and in failure (see below), your entire septic system would back up as you used the building drains, and you'd see drains backing up into the lowest areas of the home like a basement toilet or sink. I don't mean odors, I mean sewage backup.
• Partial septic blockage:
  
  If a building drain or septic system or system drainfield is partially blocked, it's possible for that condition to generate odors in or out of the building.
  
  In this case odors often correspond to surges in system use, and odors should not correspond particularly to cold weather, except insofar as cold still air may permit gases to fall (from a plumbing vent stack, for example) , or different seasonal wind patterns may cause gases to move to areas where they're not noticed in warmer weather.
• Are the plumbing vents blocked by snow cover or frost? 
  
  That's a common source of sewer or septic odors indoors, gurgling drains, trap siphonage and poor drainage.
  
  See PLUMBING VENT BLOCKAGE ODORS
  and
  See PLUMBING DRAIN NOISES where we explain the basics of proper plumbing vent piping and how errors cause trap siphonage, odors, and noises

Cold Weather Sewer/Septic Odor Clues that Do Not Point to a Frozen Drainfield

If you're using the building plumbing, drain, and septic system and it's not backing up it's not so likely that the problem is a frozen septic field.

There could be a drain vent line problem such as a frozen vent line (frost from moisture moving up the vent line above the roof from use of that drain for laundry or showering).

Be sure the traps in the lower bath are not dry as a dry trap will often send sewer gases into a building.

Cold Weather Sewer or Septic Gas Odor Sources

Check out the above items first. But take a look at these cold weather sewer gas or septic gas sources that may show up more noticeably when temperatures outside are falling or when the outdoor air is still such as in evenings.

• Blocked septic systems:
  
  The photo shows red septic dye in the snow during our test of the septic system shown in the photo at the very top of this page.
  
  This septic system was in failure, as indicated first by the septic loading and dye test (with less than 50 gallons of water run into the septic system in this case. The septic absorption field would not accept any effluent not due to freezing but because it had become saturated and clogged.
  
  In fact the combination of home-made too-small septic tank, no working effluent distribution system, a septic effluent pump that sprayed effluent on anyone nearby when it operated, and sewage flowing to the yard surface, this unfortunate property had no working septic system at all.


• If a septic tank is blocked,
  
  outdoor drain lines are blocked, broken, or clogged, or if a drainfield has failed and won't accept septic effluent, the system may partially back up when loaded (extra visitors, doing laundry), and is well on the way to a complete failure requiring further diagnosis, drain repair, tank repairs, or field replacement.
  
  A sluggish septic system 
  
  can also cause septic gas backups in buildings. If the septic tank is blocked because of a failing drainfield, pumping the septic tank may give temporary relief - and a false sense that the problem has been fixed.
  
  See SEPTIC INSPECTION & TESTING


• A blocked septic tank outlet baffle 
  
  can cause sewer gases to back up into the building drain system any time, cold weather or not. Pumping the septic tank may "cure" this problem by removing the blockage at the tank outlet, but we suspect the building also has a leaky or defective vent piping system or leaky defective toilets or fixture traps as well

• Sewer/Storm Drain Flooding: 
  
  Tracked indoor sewer gas odors to a combination of wet weather, flooding sewer and storm drains, and backdrafting in the building due to improper bathroom exhaust fan vent installation
  
  See - BACKDRAFTING & SEWER/SEPTIC ODORS This article describes sewer odors due to a combination of wet weather and building back-drafting.

See PLUMBING VENT DEFECTS & NOISESfor diagnostic details of venting problems

and see PLUMBING FIXTURE TRAPS for fixture trap inspection and defect diagnosis.

Also see METHANE GAS SOURCES and

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.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Reader Question: septic issues in Connecticut during cold weather

Do you know of someone in the southern Connecticut area that has extensive knowledge about troubleshooting septic issues?

I have had 3 different septic companies and 3 plumbers to my house and no one seems to be able to troubleshoot the problem.

Cold weather sewer odor symptoms:

• have a walk out basement that is below grade.
• Basement Shower, Washing Machine, 2 sinks and toilet all feed to what I was told is a dry well.
• 1 person uses the Basement Shower, Washing Machine, 2 sinks and toilet on a every day basis.
• There is a strong gas like odor in the basement and the above located master bedroom when a lot of water is ‘used’ in the basement.
• This problem has existed since I moved into the house 8+ years ago.

For example, when the shower is used for more than about 3 minutes.

When the toilet is flushed several times and the sink is used to wash hands within a short period of time.

This ONLY happens when it is cold outside (below 40 degrees or so).

There is no smell when the temperature outside is above 40 degrees or so.

One of the septic companies removed the toilet and ran a camera and checked the structural integrity of the line.

He also dug to inspect the dry well and said that there were no issues that he could see.

He then had the dry well cleaned out. Since I didn't even know that this dry well existed, it had been 8+ years at least since the dry well had last been cleaned out. The clean out was performed in August 2013 and the gas odor returned in October 2013.

Since all the basement utilities are used daily, lack of water in the traps has been ruled out as an issue.

I have not been able to identify if there is a vent for the basement.

The rest of the house is on a separate septic tank and there are no issues with that. - C.E.T. 12/10/2013

Reply:

At https://InspectAPedia.com/home_inspection/Home_Inspectors_Directory.php you might find an experienced home inspector who has septic system expertise too, or who may be able to make a competent suggestion - offer to pay them for a brief consult if necessary. I presume you've checked out the cold weather septic odor article beginning above

at SEWER GAS ODORS in COLD / WET WEATHER  ?

It's too bad but true that often to get competent help we have to learn something about the problem ourselves.

I'd be sure to rule out the obvious (loose toilet, slow drains, frost-clogged plumbing vent) before doing anything expensive.

If there are un-vented plumbing fixtures in the basement that's certainly likely to be a year-round problem not just a winter problem;

Ask yourself what's different in winter - not just that it's cold outside, but that the heating system is on, windows are shut, in sum: the air flow patterns in the building change, and there may even be backdrafting due to closed house plus operation of heating equipment (which would be unsafe).

And re "Since all the basement utilities are used daily, lack of water in the traps has been ruled out as an issue."

If there is a basement floor drain that connects to the sewer or other drain line, it can indeed run dry any time, or may not even be properly trapped. Try to narrow down the odor source by odor strength, time of day, equipment on or off, doors open or shut, etc. 

Reader follow-up:

I was able to find the source of the smell by running the shower for a long period of time and then seeing where the odor was coming from first.

The odor is coming from the hole where the white tube that is running from the washing machine goes into. I imagine that the hole, which I am sure leads to the dry well, is not trapped or not trapped properly. I attached a picture.

[Click to enlarge any image]

Reply:

Indeed it is not uncommon for an installer to fail to properly trap and vent a washing machine drain, and drywells, while not usually as smelly as septic tanks, can send odors back into a building.

Pending opening the wall to inspect the piping and install a proper trap on the washer drain you could stop odors from entering at the washer drain hose connection by makeshift-sealing the connection between the flexible washer drain and the pre-fab drain connection shown in your photo.

Reader followup:

Thanks, I was wondering if there was a way to seal it instead of opening the wall.  I will call a plumber and see what he can do to make the seal. 

Reply:

First try a simple DIY project - you can use a bit of insulation and duct tape - just be sure you don't drop insulation or crud into the drain as you may block it if you do.

As a seal in this location is non-standard, your plumber won't be any smarter than you are. And I would NOT use caulk or something that would glue the washer drain hose to the connection or it'll be hell to remove it later.

Reader follow-up:

Ok, thanks for the tip.  I will give it a try.

and see PLUMBING FIXTURE TRAPS for fixture trap inspection and defect diagnosis.

Also see METHANE GAS SOURCES and

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.

 

On 2018-12-18 by Kim

Thank you

On 2018-12-17 by (mod) - smell sewer gases at the outlet opening of a plumbing vent pipe.

Kim

Yes it's normal to smell sewer gases at the outlet opening of a plumbing vent pipe. That's in fact why proper installation requires the pipes to place their final vent opening above the roofline.

However it's quite abnormal to find the vent line full of water. Unless you could actually see all the way down a vent to a plumbing trap that suggests to me that there's a blockage or something is wrong and you need a plumber to investigate further.

On 2018-12-17 by Kim

Greetings - Is it normal to smell sewer odors at the top of a sewer vent pipe? I feel like this is a really stupid question because common sense tells me that, yes, if you stick your nose into a sewer vent pipe you will smell sewage gases.

Background: Just had roof repair done and roofer raised concern that the sewer vent pipe might be blocked because he could smell sewer gas in the sewer vent pipe. He also said he looked inside the pipe and it was "full of water".

I went on the roof after he left. I saw no standing water in the pipe, though there was some condensate since we do live in a cold climate. I sent a 16 foot plastic pole down the vent pipe (used for apple picking) and detected no obstructions all the way down to the point where the vent originates in the basement

I did, though, smell sewer gases if I literally stuck my nose over the end of the vent pipe.... Thanks for reading!

On 2018-01-27 by (mod) - ice is forming from sewage effluent on a septic mound

Anon

If the ice is forming from sewage effluent that suggests that the mound is no longer working acceptably.

You may need to wait for better weather to get more detailed diagnosis and a bid on repair or rebuild; an inspection in the septic tank or D box can tell you if the system is also backing up - risking a sewage backup indoors.

On 2018-01-27 by Anonymous

I have ice formations on 2 sides of my septic mound

On 2018-01-08 by (mod) - using root killers in the drainfield

No, Cindy. See ROOT KILLERS in SEWER LINES or SEPTIC PIPES https://inspectapedia.com/septic/Root_Killer_for_Soakaway_Beds.php for details about products like the one you named.

My diagnostic and thus repair suggestions for cold weather septic gas problems are in the article above.

On 2018-01-08 by Cindy

Will rid x get rid of septic gassed during the extreme cold weather ? If not what will ? This only happens during cold snaps when below 30 degrees

On 2017-12-30 by (mod) - sewer smell from air ducts on cold nights

Have the duct interiors been inspected for leaks or animals?

On 2017-12-29 by r cook

We have been experiencing a sewer like smell for two years now, only on very cold nights (never during daytime even if it is very cold and heat is pumping). And only coming from certain heat ducts in the house

On 2017-09-09 by Barb

We've been experiencing an ongoing nasty sewer gas smell whenever our toilet is flushed - moreso in the cold/wet/winter weather than in the warm summer. The vent pipe on the roof is not blocked. We replaced the toilet seal a couple of times, the last time with a wax ring.

We did have a plumber out and he added another wax ring to the one one we had recently installed. After he left, the smell was GONE, (this was in cold January) but it only lasted for 2 weeks, after which the smell returned. It seems like the problem is the toilet seal - we're just not getting a good seal....

can anyone recommend a product, or procedure, that will work? We have also tried the rubber/vinyl type gasket seal, which didn't work either. Cold weather is coming and we're starting to get a hint of the bad smell again....need to fix this before it comes! Thanks.

On 2017-06-01 by (mod) - occasional odor with from an aerobic septic system may be normal

From our readers who use aerobic septic systems, and from the manufacturers literature, I have learned that an occasional odor with from an aerobic system May in fact be normal. I do not recommend using any septic additives such as the one that you named.

There are some Aerobic System designs that do require specific additives named by the manufacturer. So we would need to know the manufacturer and type of your system to research further.

On 2017-06-01 by Greg

I have an aerator septic system and at times I can smell a wisp of the septic tank. After opening the cover the system looked normal except the waste looked thicker than normal even though the air was pumping through as normal.

The discharge water looked clean as always. I just had it pumped off last year. Is there something else I should be doing. I haven't used any Rid X or anything like it.

...

Continue reading at SEWER GAS ODORS in COLD / WET WEATHER or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Sewer & Septic Gas Odors Articles

• BACKDRAFTING & SEWER / SEPTIC ODORS
• BUILDING DRAIN ODOR SOURCES
• PLUMBING VENT BLOCKAGE ODORS
• DRAIN LINE SEWER ODORS
• DRAIN PIPING & SEWER ODORS
• DRAINFIELD ODORS, FAILURES
• FIXTURE vs SYSTEM DRAIN BLOCKAGE
• FLOOR DRAIN / TRAP ODORS
• GAS DETECTION INSTRUMENTS
• INDOOR SEPTIC ODOR, OUTDOOR CAUSES
• METHANE GAS HAZARDS SEPTIC / SEWER
• ODOR EVENT / SOURCE LOCALIZATION LOG
• OTHER ODORS BLAMED on SEPTIC / SEWER
• OUTDOOR SEWER ODORS
• PLUMBING FIXTURE TRAPS
• PLUMBING VENT BLOCKAGE ODORS
• SEPTIC SYSTEM ODOR CURES
• SEPTIC / SEWER ODOR SOURCE TABLE
• SEWAGE ODOR SOURCE LOCATION
• SEWAGE PUMP ODORS
• SEWER GAS ODORS
• SEWER GAS ODORS in COLD / WET WEATHER
• SEWER GAS ODOR REMEDIES
• SITE WEATHER or NEIGHBOR'S SEWER ODORS
• WET WEATHER SEWER ODORS

Suggested citation for this web page

COLD WEATHER SEWER ODOR SOURCES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to DRAIN SEPTIC SEWER PIPES

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