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ODORS GASES SMELLS, DIAGNOSIS & CURE
PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
ANODES & DIP TUBES on WATER HEATERS
BACKUP PREVENTION, SEPTIC
BACKUP PREVENTION, SEWER LINE
BACKWATER VALVES, SEWER LINE
CHEMICAL CONTAMINANTS in WATER
CHEMICAL ODOR SOURCES
CHLORINE IN DRINKING WATER
DEPTH of SEPTIC TANK
DRAIN & SEWER PIPING
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR DRAIN / TRAP ODORS
GAS PIPING, VALVES, CONTROLS
HARD WATER - SOFTENERS
METHANE GAS SOURCES
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
ODORS, SEPTIC or SEWER
ODORS SEWER GAS in COLD WEATHER
ODORS, SULPHUR SMELL SOURCES
ANIMAL or URINE ODOR SOURCE DETECTION
PIPING IN BUILDINGS, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING NOISE CONTROL
PLUMBING VENT DEFINITIONS & CODES
PLUMBING VENT DEFECTS & NOISES
REPAIR BURST LEAKY PIPES
METHANE GAS HAZARDS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
WATER TESTS, CONTAMINANTS, TREATMENT
WINTERIZE A BUILDING
Cold-weather-related sewer or septic system odors: this article describes how to diagnose and correct sewer gas or septic odors (and other building smells and odors with focus on diagnosing odor sources and causes in cold weather. This article on diagnosing sewer gas or septic odors is a special cold-weather edition of our more general advice on finding and curing sewage odor problems. Here we focus on sewage or septic odor problems that occur during cold weather or wet weather.
Also see Backdrafting & Sewer/Septic Odors This article describes sewer odors due to a combination of wet weather and building back-drafting. 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. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
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. Our sewer gas odor diagnosis articles are grouped into SEWER GAS ODORS and SEWER GAS ODORS in COLD WEATHER - the article found below on this page
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.
Tips for Tracking Down Hard-to-Find Sewer Gas Odors in buildings
Other Sources of Sewer Gas or Methane Gas Odors in buildings
Others with whom we have worked on tracking down sewer gas odor problems have taken these steps to successfully track down and fix the source of cold weather sewage odors in or around buildings:
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs) on tracking down cool weather and night time sewer gas / septic tank smells
Question: on cool summer nights we smell septic gas, always at the same place, how do we fix this odor?
Have septic system in mountain area of NC. Only on COOL summer nights do we smell septic gas (always in same place) at rear of house. Also noted that either dishwasher or bathtub or washing machine is emptying into system when smell is detected.
The roof vent pipe is located on backside of house roof where we detect the smell below. Have concluded that smell is associated with vent gas being displaced by emptying water from an appliance and since outside air is COOL the gas "falls" to ground level where it is detected.
Do you have any thoughts on what might be causing problem? If agree with my conclusion there are vent mounted activated carbon filters that mount on top of vent pipe that are claimed to solve the problem, any comments will be appreciated. - S.T.
[Our photo at left shows a common source of septic gas odors at an older home. This add-on plumbing vent may be a bit too close to that bedroom window, and also in cool weather its exhaust may be noticed by people on the ground below or on a nearby deck.]
Reply: Cause and Cure Suggestions for Septic Tank Smells in cool evening hours
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem in the septic tank, drainfield, or plumbing venting system. That said, here are some things to consider:
A basic tenet of tracking down odors is just what you have done - relate the smell to other conditions like time of day, weather, etc. Without knowing details about your home I am just speculating:
If you have a slow plumbing drain, a sluggish drainfield that is failing, or a plumbing vent defect, pushing water into a drain at high rate can in turn result in an increase in the level of sewer gases (or septic tank gases) that are back-venting up the drain/waste/vent piping. Those gases should vent through the roof and should not be noticeable to building occupants.
But in the cool of evening not only do temperatures fall, but typically wind velocity falls as well. Under those conditions even a modest smell problem can become more noticeable because the gases are not being dissipated by air movement, and may even be falling towards ground level as escaping plumbing gases are cooled in the night air and, counter intuitively, might even ride descending air currents that during warmer daylight hours, would instead be rising air currents.
Your suggestion of adding a filter to try to reduce odors is a band-aid approach that has some risks: you might be better off to track down the odor source to see what it means. For example, improper plumbing venting can be unsanitary or even dangerous; and obtaining an early warning that the septic drainfield is failing may be useful in planning for repair or replacement of the system.
Tracking Down Sewer Odors Outside
Because you notice the odor at a particular location - at the rear of the house, and at a particular time - in evenings, that's a good time and place to start tracking the odor to its source.
If by "rear of the house" you mean outdoors, sniff towards the septic tank, drainfield, or any sewer line vents (see our photo at above left) or sewer line cleanouts that might be installed between house and septic tank.
Tracking Down Sewer Odors Inside
If you meant that the odors are noted inside the house, see if you can track the smell to a particular room or plumbing fixture or drain. Sometimes we find that sewer odors are traced to a leaky plumbing drain, loose toilet, or even a poorly connected dry plumbing vent running through the ceiling.
In both old and new construction we also occasionally come across an orphaned drain or waste vent line that was just chopped off and forgotten (photo at left).
A plumber can pressure-test your drain-waste-vent piping if that step becomes needed in tracking down the odor.
Also remember to have an expert take a look into the septic tank to see if it's sewage level is normal, if the baffles are intact, etc.
See SEWER GAS ODORS for our checklist of sewer gas or septic smell odor track-down details.
Question: neighborhood sewer gas smells
our whole section of town often smells of sewer gas! it is noticeable for 2 or 3 blocks. what's up with that? p.s. - most often is worse when it cools down after a warm day or during the monsoons.. - Sharon 7/22/11
Sharon when there is a sewer odor in the neighborhood, if your homes are on private septic systems I suspect someone's drainfield is in failure. If we're talking about a community where every home is connected to a municipal sewer, there could be a burst line, effluent breakout, a problem with a pumping station, or the odor could be from something else.
Question: cesspool odors that stop when the rain stops - smells during heavy rains
I would like an opinion. I have a cesspool, it has been pumped out even though the gentleman said it did not need it. Every time we have heavy rains in our area I get a foul smell inside my home;. when the rain stops the odor goes away. I had it pumped thinking that was it but the cesspool man said it was not Can you give me any idea of what it might be the system was installed in 1964 and even though old still works perfectly with this one exception. Thank you - Carol 8/15/11
Question: bad sewer smell early in the morning - landlord says system needs to be broken in
We moved into a doublewide in western NC last March. We noticed, mostly late evenings and early mornings, a really bad sewer smell. Our landlords said that sometimes, as a system gets used to new people and new system uses, it can be a little smelly. Anyway, soon, spring and then summer arrived and the smell had gone away completely. At the very first sign of fall, however, the smell has returned. Now that all of our nights are in the 40's or below, we are smelling it again every morning and evening, but not during the heat of the day when temps reach the 70's. There is no smell coming from inside the house, only what drifts in through open windows. Everything seems to drain fine in the house. Totally clueless and really frustrated at this point. - Jeff 10/6/11
Question: smell in unfinished bathroom
I hope that some help be given as we are at our wits end. I have and unfinished bathroom in the basement
Question: sewer odors coming out of interior perimeter drain in dry basement
Ok I have an issue... I own a bi-level home. One of the bedrooms is in the lower level. The entire lower level is finished. There is a french drain that run around the entire basement, however most of it is covered. There is no water, nor has there ever been any water in the drain. Over the past week, out of the blue the odor that is coming from the drain is mind blowing. It smells like ammonia and other things. The room that smells is closest to the septic tank. Thinking that there might be a problem I had the tank emptied and still no relief from the smell... When it rains the smell only gets worse... Any suggestions on what I might be looking at. - Brian D 11/29/11
Brian, on occasion I've found that a leak in the sewer line or even at the tank itself it it's near the house can leak into the foundation drain or perimeter drain and even enter the basement. As you've not seen a problem at the tank itself I'd check the condition of the sewer line between the house and the septic tank next.
Question: raw sewage odors in very cold weather
I read your article and I would like to explain my problem to see if I have come up with the problem. I live in Cheyenne Wyoming and when it is very cold (below 25 degrees Far.) we get a very strong raw sewage odor from our basement bathroom. I have narrowed it down to the bathtub. We did not finish the basement, it was finished when we moved in. The odor was not disclosed to us when we moved in 3 years ago and this winter it is worse but it is colder. We have smelled it every winter since we moved in. Now tonight I decided to try an experiment. I closed the drain on the tub and put water in the tub and this seemed to fix the problem. So my opinion is that they did not put a "P" trap on the tub. So what do you think?
There may be a corroded leaky P-trap that thus doesn't maintain its water seal. Try pouring water into the trap and inspect with a good light to see if it remains in the drain; Unfortunately some demo and digging may be in order to fix this odor source.
Question: septic tank under the garage
OUR SEPTIC TANK IS LOCATED UNDER OUR GARAGE WE HAVE A SEALED HOLE WITH A CAP ON IT DURING THE COLD MONTHS WE GET A SEWER SMELL IN SPECIFICALLY ONE PART OF OUR BATHROOM ITS THE AREA WHERE ALL THE PIPES ARE LOCATED THE TOILET SHOWER AND SINK WATER ALL GO INTO THE SEPTIC TANK WE TORE UP OUR FLOOR AND REPLACED ALL THE PIPES WE HAD OUR TANK CHECKED ITS WORKING FINE NOT MUCH IN IT BUT AS SOON AS IT GOT COLD IT STARTED TO SMELL DO YOU HAVE ANY IDEAS WHAT WE COULD DO - Cheri 1/14/12
oh why do people type in all caps.
A septic tank under a garage floor sounds like a bad idea to start with - but in any case if it smells the system may be backing up; check for drainfield flooding;
Watch out: accumulated sewer gases indoors (in your garage) can cause an explosion or can be an asphyxiation hazard - i.e. fatal
Question: septic works but smells when it's cold and damp outside
I have a septic system that works fine, however I have an unpleasant odor. ..usually when its cold and/or damp outside. I originally had a single wide mobile home then moved it out and put in a double wide....that's when the problems started. I've tried everything with no luck. I've tried suggestions from plumbers, had plumbers out and no one can narrow down what the problem is.
When the double wide was installed the plumber put in a clean out trap....could that be part of the problem? I had the tank pumped in the summer and it seemed to help....but not get rid of the problem. I'm now trying to sell my house, but can't sell until this issue is resolved. Please can you offer any suggestions for me.?
When you changed your mobile home, is it possible that someone drove across and crushed a septic drain line or damaged the drainfield?
Question: sewer gases when weather turns cool
After a change in weather to cooler temperatures, we are smelling sewer gas which we believe are coming from both bathrooms. My husband says the bathrooms are on separate ends of the house. The smell of gas is throughout the house. - Gail Gilbert 9/10/12
Gail, check the odor track down suggestions above
Question: odors from mobile home worse when furnace is running
My furnace in my mobile home sits in front of a lot of my plumbing in the bathroom. i believe because as the weather gets colder, we use the furnace, and then that's when it smells the worst. i have also noticed that while the furnace is running and then run water in the kitchen, its the worst! - Anon 10/31/12
Look for a blocked or missing plumbing vent that is causing drain gases to back up out of a drain near the furnace return air intake
Question: sewer smells near washer during heavy rain
Last may I installed a washer in the basement. Everything has been fine until we had over 6 inches of rain during a 24 hour period back in September - at that time, I noticed a septic odor in the basement and also in the cabin. Since then, the odor has appeared during cold damp weather, but only in the basement. I don't smell anything outside, just in the basement. My tank was cleaned out four years ago and I live alone, so I would think the tank is fine. Before calling the septic service and spending money I don't have to spare, I would appreciate your opinion and suggestions. - Diane 10/31/12
Check our suggestions about bad plumbing vents as well as flooding septic systems in the sewer gas odor article links found at page top
Question: sewer gases picked up by furnace during cool weather
Now that the weather has turned cooler and the furnace is on, we are experience sewer smells thru the heating floor vents on the upper levels of the house. We also have smelled the same odor from the drain in the basement bathtub. There was no odor throughout the summer or spring months. Can't figure it out so far. - Deborah 11/17/12
Reply: check for sewer gas draw into cold air returns; try using a sniffer person or a TIF8800 combustible gas detector
Deborah, if sewer gas odors come out of heating supply registers I suspect that sewer gas is being drawn in at a cold air return. That may help you start looking.
Last winter we had $10,000 worth of drain work done to replace the old clay ones under out house. They put in all new clean outs to meet regulations. This was done in December and we survived the winter season without any problem with sewage smells, although it was fairly mild. Prior to this work being done our daughter lived in the basement for at least 10 years without problem.
We called the drainage company who did the work back and he checked all the drains for P traps and dry/wetness. He claimed all was fine. Could it be the old city pipes coming into our new connection that might be a problem? Thanks for any and all help. We are in the process of getting someone to climb our roof to check the stack for some kind of animal blockage (nest) perhaps. It's driving us crazy. The contractor said to call him back if the smell still persists which we will do. - Deborah 12/5/12
Question: steps in tracking down & curing sewer gas odors occurring only in cold weather
I am pretty much at my wits end with the sewer gas smell that enters the mail level of my home when the temp outside goes below 30 degrees. It is very upsetting because the smell is not pleasant and is most pungent near the kitchen window. The smell continues along that same wall into our living room and family room. My husband already went up on the roof to pour a gallon of bleach and then several gallons of water down the vent pipe. Nothing changed. Also, we had a plumbing service come out and no resolution there either. Help please. - S.N. 12/6/2013
Please first check out the article above on this page; let me know what questions remain and what has been done or checked so far and we'll pursue specific details for your home.
I did read your article through before sending you my question. The only addition is that we had another plumber out again yesterday and he was very perplexed by our situation. He suggested that we first put a turbine exhaust fan over our roof plumbing stack. He thinks that will help pull the air through. If that does not work, he wants us to apply heated tape to the pipe in the attic leading to the roof plumbing stack. If we do that, we will need to add in an electrical outlet in the attic to plug in the heated tape. Honestly, we are not too sure what to do. Your advice would be greatly appreciated. - S.N.
The added detail in your note lets me comment further with some diagnostic suggestions: While we might on occasion apply a band-aid to a problem as a temporary fix, generally it is better to find the cause of the plumbing problem instead. If the house is old and the odor problem is new, then the best approach is to determine what has changed or broken or come disconnected or blocked so as to cause the odor.
Adding a fix atop an existing problem without understanding the problem cause risks wasting time and money and risks failing to attend something important but not immediately obvious. Put another way, we can spin our wheels applying one band-aid after another without any success because we never took time to figure out what's wrong. Therefore
Borrowing from our general approach to tracking down odors to their source here are some additional diagnostic suggestions:
Keep an odor log, noting when and where odors are worst (you already cite the kitchen area). Relating odors suspected to be due to plumbing vent frost-clogging to outdoor temperatures, wind, and fixture use could be diagnostic.
Note carefully where odors are worst: outdoors vs. inside (on occasion area wind patterns send plumbing vent gases down from a properly-working rooftop vent to lower building windows) and inside by room, fixture, and fixture use.
Often plumbing or sewer gas odors are ultimately traced to a loose toilet, a clogged drain, or an improper plumbing trap. But if we are sure that at your home the odor problem is new, and only a cold-weather problem, I suspect that the problem will be traced to something that has changed, such as a drain that is partly blocked, a vent that is partly blocked, a vent that has come disconnected somewhere in the building (it was never properly glued or soldered, or it was punctured or damaged) or similar damage to a building drain.
Keep me posted and we'll take it from your next report.
My husband just left Home Depot and got the heat tape, but will hold off after reading your response below. We have 2 toilets upstairs that keep running. One flushes on its own during the night and the other takes forever to complete a flush. Should my husband replace both toilets or should he just repair them? We need to address this soon because the weather just dipped again to 16 degrees and the smell which was gone for 2 days is back in full force again.
Here's where I'd start:
1. if you can't quickly fix a running toilet (you may need to replace a flapper valve or the fill valve) then turn off the water supply to the toilets that are running. IF there is no toilet shut-off valve, most likely you need a plumber to add one - at which case you'd also at the same time replace any parts needed to stop the running toilet problem in the first place.
2. If the drain is not totally blocked you can often remove the partial ice blockage it by running very hot water down the drain for a time.
Matt did a bunch of plumbing work on a bathtub & 2 toilets upstairs. He is off tomorrow from work and will be continuing his repair efforts. Once Matt has completed everything, I will let you know if the odor dissipates during cold weather. Thanks again Daniel for your awesome guidance and feedback.
I have no news to report yet. We have had 30 to 40 degree weather for several days, so the odor has not been present in the house. The weather is going to dip below 20 degrees again though. I can then see how things go with the cold weather odors. I am hoping all the plumbing repairs Matt did on the 2 toilets and bathtub upstairs make a beneficial difference. If not, Matt is going to wrap the pipe in the attic in electrical wire (heat tape). As soon as I have feedback, I promise to let you know. - M & S N 12/23/2013
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:
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
At http://inspectapedia.com/home_inspection/Home_Inspectors_Directory.htm 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 my cold weather septic odor article beginning above at SEWER GAS ODORS in COLD 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.
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]
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.
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.
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.
Ok, thanks for the tip. I will give it a try.
Questions & answers or comments about diagnosing the source of septic or sewer odors in cold weather
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