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Plumbing vent beginning to clog with snow (C) Daniel FriedmanCold or Wet Weather Sewage or Septic Odors

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. We also discuss causes and cures for sewer gas odors related to wet or cold weather. We include questions & Answers on tracking down cool weather and night time sewer gas / septic tank smells.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Sewer Gas Odor Tracking by Site Location and Season or Weather

Photograph of melting snow indicating septic tank locationArticle Series Contents

Where on the property are odors strongest?

you may be able to point to a waste line, building exit piping, leaks at a septic tank, drainfield failure, or even a neighbor's septic system problem.

Look for a wet area, possibly covered by snow in northern climates - kick the snow aside in a grid pattern over the septic system components (don't' fall into a collapsing septic system - it can be fatal).

Look for areas where snow has melted to a thinner cover. This can occur in a normal system (bacterial action in the soil over the septic system and warm septic effluent carry heat out of the septic tank). But it can also be a clue of sewage effluent coming to the surface. Check such areas for effluent.

If a waste line is blocked or partly blocked and the odors are near the house, such as at the house wall at the waste line exit point, effluent could be running along the buried pipe but outside it, having leaked from a damaged pipe at the wall, between the wall and the septic tank, or at the tank itself there could be an effluent leak where the line enters the tank, or at the tank cleanout top cover (which would indicate a blocked tank outlet or blocked drainfield).

Effluent will follow a buried pipe because it runs in a trench dug in the soil - the pipe and backfill in the trench are less solidly packed than in the surrounding soil - the trench acts as a conduit to bring sewage effluent to the house if the trench is filling with liquid.

Broken sewer pipe (C) Daniel FriedmanBroken pipe leaks may be mistaken for ground water leaks:

At left we show a broken sewer pipe found by lifting a section of sidewalk in a soft smelly area of the yard.

At a different property where basement paneling was removed following "a history of basement water entry from 'rising ground water' (according to the basement de-watering company)" a company had installed an expensive interior trench and drain system and sump pump to pump the "ground water" away.

We saw an inverted "vee" of leak stains on the basemen wall extending from below the main waste line where it exited the building.

It was obvious that the water entry had been not from rising ground water but from a broken leaking waste line outside the wall. Sure enough, our septic dye appeared in the new basement trench and drain system in just a few minutes.

The basement de-watering system had not been needed at this home, and the owner still needed to have the broken waste line excavated and repaired.

Look for leaks at a waste line, perhaps first by having a plumber snake the line from inside the building to see if s/he feels evidence of a broken or collapsing or damaged pipe between the house and the septic tank.

See SEWER LINE REPLACEMENT (includes How to Find Distance to Drain Blockage)

If the drain field is saturated or blocked, expect to find abnormally high sewage level in the septic tank, possibly even backing up and flowing out when the tank is opened, and possibly also evident at the distribution box.

See SEPTIC TANK INSPECTION PROCEDURE

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-10-16 by InspectApedia (Editor) - sewer smell in my house

@Debbie,

Particularly in winter, when, if my surmise is accurate, your home's windows are closed, if you smell sewer gas indoors, the problem is not so likely to be due to roof pitch and outdoor wind conditions that might cause an outdoor down-draft of odors from the rooftop plumbing vent.

But as you'll read above on this page, the colder temperatures of winter can explain why some odors appear only in cold weather. For example, if there were a leaky plumbing vent connection in the walls of your home (in that entry closet wall?) it might be that only in winter when outdoor air is cold, might rising sewer gases in the vent system spill out of a leaky joint rather than rising by convection and exiting at the rooftop.

A plumber can pressure test your drain and vent system for leaks, but before going to that expense I'd first check the more-obvious sewer gas smell sources like a loose toilet, bad toilet wax ring (are odors strong if someone, on hands and knees, sniffs near the base of the toilet?), or from a dry plumbing trap in that nearby bathroom (does the odor dissipate if you run some water into each of the traps?).

Watch out: don't assume that there could be no fuel gas leak just because you have not yet turned on your heat.

Fuel gas leaks (LP or natural gas) can be present anywhere in the gas piping system, and might be noticeable only in cold weather when the building is less ventilated.

On 2022-10-16 by Debbie

Every winter for the past 7 years I have a sewer smell in my house. I don’t know if it’s a coincidence but it started the winter after we remodeled the outside of our house.

We had a steeper pitch roof put on and I’m wondering if the smell is coming from a downdraft on the vent. The smell is strongest in an entrance closet closest to one of the bathrooms and to the outside part of the house.

My husband always fixed things, but he was diagnosed with cancer at the end of the remodel and passed away four years later.

I have no idea who to even call, but I’d love to fix this problem. I know it’s not an LP gas leak because the smell started to smell before I turned on my heat this year. Any help is greatly appreciated.

On 2021-11-29 by Inspectapedia Com Moderator - inspection of the sewer piping and vent piping using a sewer line camera

@Melissa,
An inspection of the sewer piping and vent piping using a sewer line camera might be worthwhile and also a review of the buildings leak history to address the question of whether there could be mold contamination in a wall floor or ceiling cavity

On 2021-11-29 by Melissa

We have a horrible smell like dirty diapers and almost hurts a bit to breathe that happens after the shower is used in one bathroom and only during cold weather.

The smell completely disappears during spring and summer and didn't start up again until we started needing to turn on the heat (like when it hit below 60 degrees outside but not freezing temps.)We can smell it coming from the shower drain but we also sometimes smell it in other areas likely the wall behind the toilets.

The master bathroom is on the other side of this bathroom and has a window that we have to keep open at all times during winter or smells back up in there too.

We've tried everything so far: septic pump, adding vents to plumbing in basement, putting hose down vent pipe on roof to wash out anything that might be in there (black water backed up in sinks, is that a clue?), adding sweet air filter to vent pipe (made it worse so we took it off), vinegar/baking soda down all the drains, draino in case of clogged pipes.

The house was built in 1967 and does not have PVC. We're on a septic and well. Looking for any possible solutions and I'm scared it may be a damaged vent pipe in the walls.

On 2021-10-27 by inspectapedia.com.moderator

@Anonymous,

Great, that will help other readers.

About tracking down indoor odors, the rooftop vent is not a likely source unless

- it is not properly plumbed, sealed, connected as it passes up through the building

or

- there are downdrafts of outdoor air containing sewer gas that also leak into the building interior

But a deflector or other plumbing vent device (such as an odor filter) can reduce outdoor odors of downdrafting sewer gases.

On 2021-10-27 by Anonymous

@inspectapedia.com.moderator, we just purchased on amazon. I will let you know if we see improvement. Thanks!

On 2021-10-25 by inspectapedia.com.moderator

@Anonymous,

Look for a high-wind cap for plumbing vents or a plumbing vent wind diverter; an example is made by Camco, their "Camco Cyclone Plumbing Vent " often used on RV plumbing system vents and shown below.

Also see products like the OdorHog sewer vent or plumbing vent cap claiming to prevent odorous downdrafts from rooftop plumbing vents;

You'll see that the manufacturers of ALL of these outdoor efforts to stop downdrafting sewer gas odors from an outdoor or rooftop plumbing vent take care to warn you that these products address outdoor sewer gas odors, not in door sewage or sewer gas odors.

On 2021-10-25 by Anonymous

@inspectapedia.com.moderator, Thanks for the quick response! You mentioned a wind-operated elbow that keep vends open facing down wind in another response. We have lots of wind out here on the farm, so I was wondering if you could tell me what kind of fitting that was or where we could buy one? Thanks!

On 2021-10-25 by inspectapedia.com.moderator - moving around odor source

@Jeremy,

I agree that a moving around odor source is difficult to diagnose.

You might look for causes of building air currents and door transport in your home such as is air conditioning or heating duct system that can pick up an order from one place and transported to another.

That can account for a remote and undetected odor source.

You might also check to be sure that the odors are only indoors and not outdoors. Outdoors you might look at site conditions including wind direction and downdrafts from the rooftop plumbing vents.

If a pressure test on the Beltline found no leaks then it's probably not worth any invasive inspecting methods such as cutting up on a wall or ceiling to check the routing of the vent line.

You're on site people respond to look for other odor sources as well, ones that may have nothing to do with the plumbing system.

Sometimes a sensitive gas detection instrument can help pinpoint an order source.

On 2021-10-25 by Jeremy

Hello,
We just built a new house this year and we have had intermittent sewage smells in the bathrooms that our plumber has been unable to figure out. The plumbing passed inspection and the pressure test.

We run water in all the drains once a week to ensure traps have water. It started in our master toilet shortly after we moved in and was strong when it rained. They replaced a gasket on toilet and that seemed to fix it for a bit. It then moved to our half bath located on main floor.

They then replaced and reset every gasket in every toilet in the house. The smell then seemed to come in the morning time from about 7 am till noon. The plumbers then inspected our propane lines for any small leaks. Found small ones but that also did not fix the problem permanently.

Now the smell is on the 2nd floor bathroom and I have not been able to find anything that drives the smell (ie rain, cold etc). I am out of ideas as is the plumber. Thought maybe I'd give this forum a try since I am losing my mind lol. Thanks!

On 2021-10-04 by inspectapedia.com.moderator - is lagoon cause of sewer smell

@Michelle Dolloff,
It would be helpful to know what country, state, city you are in as weather and climate can make a difference. If the smell is a new problem and the lagoon has always been there, it may be from another source.

If a sewer gas odor seems specific to just one area in the home one could suspect a clogged drain, inadequate vent piping, or a loose toilet or leaky vent line or leaky drain line.

We list several possible sources to review and rule out if possible at this page:

TRACK DOWN HARD-TO-FIND SEWER GAS ODORS IN BUILDINGS

On 2021-10-04 by Michelle Dolloff

We have a lagoon and our bathroom closest to it has sewer smell recently. Could it be because of the lagoon if so what do we need to do?

On 2021-06-09 by Sam - cracked cover was causing cesspool flooding

Thank you for getting back to me. The inspection cover for the cesspool had cracked along the cover so when we had flooding rains where the water table raised up in the yard 12 to 18 inches above the soil surface and then drained off when the rain subsided for about a week the liquid sewage slurry must have come out through the cracks. Some cracks were over 2 inches.

Repaired the cover. The cesspool is about 1/3 full if that. Just the toilet and kitchen sink waste water go into the cesspool. Vanity, shower and washer go into the garden. Just 2 of us here.

When digging out the black cast line the soil had a sewage smell but the sand pak a lot drier than the soil with no odor.

Soil strata drainage is excellent Not worried about health hazards as heavily hydrated limed the area and then spread a layer of mulch over the lime. Will plant sunflowers to filter the soil and hope for drier weather. Has been raining every day for months.

On 2021-06-09 by inspectapedia.com.moderator - how long until sewage odor from cesspool overflow goes away?

@Sam,

How long the cesspool overflow odor will last: I have no facts on which to give an answer with confidence, but in general, if there is a sewage effluent spill on the surface from a single event (not recurrent) then given a month of more-dry weather and no other concurrent problems like a failed cesspool itself, the odor ought to be dissipated.

Watch out: A properly working cesspool will

- not overflow onto the yard surface under any conditions

- does not flood with rainwater or surface runoff

- has a top sewage level that is 6" or more below the bottom of the inlet pipe to the cesspool (even that means the cesspool is near end of life)

So if your cesspool is flooding, even just occasionally, you will want it inspected

You will want to review

CESSPOOL FAILURE CRITERIA

and also the article above on this very page where we discuss sewage odors in cold or wet weather

let me know what you think and what questions remain; keep me posted

Thank you for the helpful question

On 2021-06-08 by Sam

I have a cesspool in my back yard. A while back we had heavy rain for a few weeks. The yard would flood out and than drain off. About 3 weeks later sewage smells began to appear. I dug out around the pump out inspection cover to inspect the cesspool and found there were cracks around the cover large enough to let sewage overflow out of the cracks.

The cesspool is about 1/2 full if that as we run our grey water into the gardens. Is it possible that the sewage affluent overflowed out of the cover during the heavy rains and saturated the soil when the water table rose.

When digging out the black cast sewer line the soil smelled of sewage and waterlogged soil. No oxygen in soil so the there is that smell also. As I was digging out the line the soil would smell but not the sand pack around the black cast pipe. Repaired the cesspool cover. I spread 150 pounds of hydrated lime on the affected area to disinfect the area.

Still have odors that waft up from time to time as the hydrated lime solution did not go very deep. Here is my question. How long do you think it will take for the smell in the soil to go away once things dry out ? Does not smell in the morning or afternoon. Just mid day when there is a breeze.

Running a strong bleach solution down the toilet to see I can smell bleach to let me know if there are hairline cracks in the sewer pipe that I may not have seen.
Thank you for your help.

On 2021-03-14 by (mod) - signs of a clogged or failed drainfield

@Kimberly,

Regardless of whether the leaks are actually right at the septic tank or elsewhere in the yard, unfortunately that sounds like a blocked, clogged, or failed drainfield.

You'll want an onsite inspection by a septic contractor or by an experienced septic test or inspection service (not just a superficial examination), perhaps using a sewer line camera or some small test excavations to find out if the repair is a simple one like a broken or clogged pipe, or if the drainfield needs replacement.

On 2021-03-14 by Kimberly - My septic tank is leaking into my yard

My septic tank is leaking into my yard. I've already had it pumped but there is still a foul odor and yard is soggy in that place. And when it rains it smells terrible.It's not leaking at the tank, but it is in my yard. Please tell me what you think is wrong

On 2021-02-09 1 by (mod)

Mary,

Thank you for your question. I really want to help and must apologize that with so little information I can't really diagnose what's wrong with the odor problem in your home. You'll need an on-site expert.

In case it helps here is a speculation: It's possible that the problem is indeed cold weather related such as frost accumulation in a plumbing vent that has blocked venting. If your venting is blocked it's possible for water to become Siphoned out of the traps found at sinks and showers and bathtubs. When you lose that water seal the sewer gases easily come up into the building. A quick fixes to make sure that there is water in each of those traps.

On 2021-02-09 by Mary

I am connected to a city sewer. It has turn very cold this last week and the smell in the house is terrible. I have run water down all drains but it did not help. What is causing this problem

On 2020-12-21 by mod) - possible odor transmission through heating ducts?

Cindy

From just the information in your text I can't say with confidence what's going on in your home.

But it sounds as if you have forced hot air heat in your home and that I know odor was coming out of the heating ducts.

If that's the case I would be looking for an older Source near the return air Inlet or a leak into the ducts themselves.

Is it an "issue" ? Yes.

Watch out: sewer gas is potentially explosive and in any event sewage odors in a building tell us that something is wrong: with the drain/waste/vent system, OR if it's a gas odor there could be a dangerous LP or natural gas leak.

On 2020-12-21 by cindy

I was getting strong sewage smells last night. Not from toilets, or sinks, but through the vents. When I went into the furnace/water heating room, the smell was stronger.

Is this an issue with the venting system, water heater or furnace. The smell stopped at about 2am. I haven't smelled it since. Not sure what was going on. It lasted for six hours.

On 2019-04-05 - by (mod) - lagoon septic odors

Red

While some odors are normal from lagoon septics, the smell ought not be apparent simply when running water into a bathtub.

I'd start by asking if the odor is from the drain/waste/vent system or if it's actually from the incoming water supply.

Sniff closer to the water vs the drains.

If it's the water supply, take a look at SULPHUR & SEWER GAS SMELL SOURCES

also this article would be useful: WATER ODOR DIAGNOSIS - SULPHUR

Since you report that both homes use septic lagoon treatment systems, it may be helpful to take a look at

LAGOON SEPTIC MAINTENANCE

On 2019-04-05 by Red

My neighbor started complaining about a sewage smell in her house but could not find the source (she and I both have lagoons)

shortly after her telling me I began to have the same smell in my house. Especially if I started running water in the tub. Is this just coincidental? If not what would be the issue and is it potentially a much bigger problem.

On 2019-02-27 by Karen Brownson

foul smell coming from kitchen sink drain only. water drains well down the drain.

On 2019-02-27 - by (mod) -

I don't know have an authoritative answer to your question but I suspect that it wouldn't hurt to clear the drain field vents but it's probably not necessary.

On 2019-02-26 by Tom Steiner

I don't have septic system issues however we have snow depths which have covered the drain field vent pipes. Not sure if I should clear the snow from the vent pipes risking exposing the field to cold. Any suggestions?

On 2018-12-30 by Anonymous

RE-posting anonymous correspondence by email:

A reader asked:

... came across your website while looking online for possible causes of backdrafting. We seem to have a foul sewer odour in our master bathroom from time to time with no particular pattern. But it’s move prevelant when the ground is soaked with rain or snow. We have a septic tank in our backyard.

I’ve had a few plumbers come to look at it but nobody seemed to have a clue. They all made guesses but couldn’t find/fix the problem.

I was wondering if you can come to look at it in Connecticut or if you could recommend what type of professionals I should talk to (roofers, plumbers, others?) to diagnose the problem? If you have any recommendations or names, I’d greatly appreciate it.

Moderator Reply

In addition to a review of the suggestions in the article above on this page,

It would be informative as well to have a septic contractor open your septic tank and inspect the septic tank level during wet weather and when you're observing the odor you describe; if the fields are failing and back-flowing into the tank that could be slowing drains or even pushing higher quantities of sewer gases back up the building drain waste vent (DWV) system;

in that case any indoor piping imperfection, even a loose toilet or bad toilet wax ring, or a dry drain or trap or outdoors downdrafts from the roof can explain a wet or cold weather odor complaint.

On 2018-06-06 - by (mod) -

Why not vent the sewer gases above the roof?

On 2018-06-02 by rm

how to fix/test sewer line vent through building exterior wall that generates gases/odors which lead to apartment window above

On 2018-01-25 - by (mod) -

I'd be tempted to ask for a pressure test of the vent piping. A smoke test will not show up a poor or leaky connection in a dry vent in a wall or ceiling.

On 2018-01-25 by Anonymous

The odor is downstairs in one of the bedrooms and hallway leading upstairs. All p traps checked , it intermittent . Really bad 4 months ago now just light in the same place . Always same place .

On 2018-01-25 - by (mod) -

Anon / Jerry:

There are both vent top filters and vent top wind-operated elbows that keep the vent opening facing downwind that can be retrofitted to plumbing vent stacks.

You don't say where the septic odor is being detected. There can be other causes.

Plumbing Vent Blockage Problems as a Source of Building Smells, Septic or Sewage Odors

This topic has moved to PLUMBING VENT BLOCKAGE ODORS - separate article

PlumbingTrap Siphonage, Dry Plumbing Traps, Sewer Gas Leaks & Freezing Weather-Related Plumbing Vent Problems

This discussion is now at TRAP SIPHONAGE & SEWER GAS

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

This topic moved to TRACK DOWN COLD WEATHER SEWER ODORS - separate article

Tips for Tracking Down Hard-to-Find Sewer Gas Odors in buildings

Please see SEWAGE ODOR SOURCE LOCATION - other Sources of Sewer Gas or Methane Gas Odors in buildings


...

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Or see SEWER GAS ODOR COLD / WET WEATHER FAQs - questions & answers posted originally at this page

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