Tracking down septic or sewer gas smells:

How to find mysterious sewer or septic smells when the source is not obvious. This article suggests things to check when you have had trouble finding the source of a sewer gas, septic gas, or methane smell in or near a building.

Sometimes the odor source is elusive because it comes and goes, is weather dependent, fixture use dependent, or because the leak is in a building wall or ceiling cavity.

Start with the inexpensive and easy things like checking for dry or defective fixture traps (or fake traps as shown in our page top photo).

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

This page lists additional sources of sewer or septic smells in or around buildings.

Also be sure to review SEPTIC / SEWER ODOR SOURCE TABLE.

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:

• Air conditioning condensate drain back-flows sewer gas:
  
  traced sewer gas smells in a building to the air handler unit of an HVAC system whose condensate drain was connected to a sewer pipe or drain / waste / vent pipe
• Battery odors:
  
  reader reports sewage / sulphur odors traced to a failed leaky backup sump pump battery in a basement
• Pressure test drain vent system:
  
  had a plumber pressure test the drain waste vent piping to find sewer gas leaks
• Toilet seal leaks:
  
  found sewer gas leaks at a toilet with a bad seal
• Leaky plumbing vent line piping:
  
  found sewer gas leaks where plastic pipes had never been properly glued in a wall
• Methane gas in water supply:
  
  found methane gas in the building water supply from public or private wells -
  
  see METHANE GAS SOURCES
• Perforated plumbing vent pipe:
  
  found sewer gas leaks where drain waste vent pipes had been perforated by a nail from flooring or in one case from hanging a picture on the wall
• Poor venting, odors at plumbing traps:
  
  found sewer gas odors at plumbing fixture traps whose water trap was lost due to trap siphonage due in turn to missing, improperly installed (too distant), or blocked plumbing vent piping.
  
  Where dry plumbing traps pass sewer gases back into a building the problem may be worse in cold weather or when building vent fans are decreasing the in-building air pressure, drawing gases out of drain piping
• Septic failure and backup:
  
  found sewer gas leaks outside due to a failing septic drainfield and/or blocked sewer piping causing backups that leaked outdoors.
  
  In a case where odors were traced to leaks at a septic tank, odors from the septic tank were strongest at the front entry door to the home, perhaps in part because the system was in failure and backing up.
• Storm Drains - Odors from flooding storm drains:
  
  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.
• Water heater sulphur odors
  
  may be due to a failed water heater anode or may be due to bacterial contamination in the water heater.
  
  See ANODES & DIP TUBES on WATER HEATERS
• CONTACT us to add other sewer gas odor sources you've found - it will help others

Question: sewer odor from upstairs laundry room; pouring water down the drain fixed it. Odors returned in cold weather.

Hi we have a newer home (only 3 years old) and have experienced a very strong sewer odor coming from our upstairs laundry room. Previously we have just poured a pitcher of water down the washing machine drain pipe and it has cleared up the smell.

Just two weeks ago we have rented the home and the renters are complaining of the foul smell but say it originates from the upstairs bathroom that shares a wall with the laundry room. We are approximately three hours away from the home but plan on checking all of the vents on the roof to see if any of the vents are clogged.

We will be moving out of the country in few weeks and would like to take care of this before we leave as we will have no control over the situation once we leave and can not afford what could possible be several costly handyman/plumbing fees trying to diagnose the problem.

I have read through all of the articles you have posted including the cold weather/rain one as the house is in Washington state and it's winter and snowing right now but any advise as to our specific situation would be greatly appreciated. Thank you for your help, Kristi - Kristan 1/16/11

oh and I forgot to mention below that we are on a gravity septic system.

Reply:

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

If the problem is system wide - that is all fixtures have drain troubles, then I suspect the main drain waste vent system or the septic system

Don't forget to check CHINESE DRYWALL HAZARDS & ODORS against the age of your house.

Question: we can't find the source of a sewer gas problem in the basement - worse in cold weather

We spoke last year about the sewer gas problem in my basement. We've lived in the house for 4 years, and this is the 4th year in a row that it has returned (typically returning when it gets cold, but we have had it occasionally in the summer).

We've had multiple plumbers, drain specialists, septic specialists, home inspectors, etc in to try to diagnose the problem and figure out where the smell is coming from, with no luck.

Would you be able to do a service call to my home? We are desperate to get rid of the smell - with a baby in the house now, we can't live here with the gas in the house. - J.E.

Reply:

I'm sorry to read you're still being plagued with cold weather sewer or septic odors. I'm not available for field investigation work. Did you take a look at the cold weather sewer gas odor article above on this page.

Reader Follow-up on tracking down sewer gas odor

[I'm looking for an expert inspector - ] I just can't think of spending more time/money on people who really don't have a lot of experience in these issues - they just check the "typical" sources of sewer gas, which we've already ruled out time and time again.

I do have one question perhaps you can answer - we have a sprinkler system. My husband went to open the valve up outside to drain the water out prior to the sprinkler guys coming to winterize.

He said that, when the water came out, it had a sewer gas smell. Have you ever heard of an instance where the sprinkler system pipes somehow are emitting sewer gas?? I can't think of how it would be possible...not sure if there are P-Traps in there or not....but I thought I'd ask.

Also, we had a plumber try to find the source by "flooding the system" with water and looking to see if there were leaks (which we didn't find any). Do you think doing a smoke test would find a problem that the "flooding the system" method wouldn't?

We had another plumber out to the house this week, and he said that he didn't have any ideas on what else to do. It is so frustrating that no one can figure this out and that my family is living in a hazardous environment.

Reply:

You might be able to get some onsite advice from one of the more senior and experienced inspectors

at EXPERTS DIRECTORY. Be sure to discuss your particular concerns with the inspector so that s/he can advise you if their skills and your needs match.

But I would also be VERY sure that the odor you are suffering is from the sewer system and not something traced to unsafe heating equipment or chimney.

Watch out: as a basic safety caution, particularly where there are gas odor complaints, be sure you have working CO and smoke detectors

Follow-up from reader:

We are sure it is sewer gas - no question about that according to the experts who have been out here. We have a Carbon Monoxide detector and smoke detectors.

Reply: smoke testing vs. pressure testing to find plumbing vent leaks

You should be able to have a plumber pressure test the plumbing vent lines - a smoke test won't do much if the leak is hidden inside a wall

Follow-up from reader:

We already had that done a year ago.  It found nothing.  I thought that it would be easier to see smoke (even if you have to cut a couple of holes in the wall) vs. finding water leaking behind a wall.

Reply:

If the pressure test didn't find a leak, and was properly done, that's important info. I'm doubtful that smoke will show up inside if the earlier test was proper though outside or at fixtures you might get a surprise. Sounds like a reasonable next thing to try.

Reader 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.

 

Reader Comment: traced sewer gas odors to HVAC condensate drain connection to vent stack

22 May 2015 T. W. Straub said:

We just found the source of our septic smell in the East Wing of our home. It appears that the HVAC contractors who installed the system on this wing plumbed the drip line from the air handler into the vent stack without using a P trap. That might have eliminated the problem, but I doubt it would be code compliant.

The way we found the problem was by using a smoke bomb in a shop vac and blowing the smoke down the vent stack from the roof. While doing that, we looked for smoke in the walls where the stacks were and then looked in the attic.

When we opened the access to the attic, we could smell the smoke (Superior #2B - 8,000 cu. ft. smoke bomb) and could see the smoke billowing out of the seams of the air handler. I hope this helps someone else out there --- Tom

Reply:
Thank you for this important comment, T.W. It's helpful to have a "real world" report confirming what experts have been telling us for a long time and that some installers or building owners simply don't accept.

The convenient shortcut of connecting the HVAC condensate drain to the plumbing stack is overwhelming for some people even though it's a bad idea. I'll add your comments to the article above and also at our discussion of condensate drain handling.

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-03-25 by InspectApedia Editor

@Rob,

Thanks for the follow-up: that will be helpful to other readers as you're describing a job done correctly.

On 2023-03-25 by Rob

@InspectApedia Editor , thanks for the notes. I checked the invoice again and they did pull and reset the toilet plus resealed with new wax ring, along with caulking. So it appears the appropriate repair was done.

On 2023-03-23 by InspectApedia Editor - proper repair would be to remove the toilet and install an new wax ring

@Rob,

Sure. IF a toilet is not well-sealed to a floor, such as because a deformed wax ring seal, the toilet may still flush perfectly-well without leaking water onto the bath floor. Only if the sewer line backs up is such leakage of sewage water likely. But the same path that isn't leaking water now will easily leak sewer gases.

So your toilet was most likely never completely sealed to the floor - you just got gas leakage not water leakage out of that defect.

The proper repair would be to remove the toilet and install an new wax ring. Caulking with silicone sealant around the toilet base will "work" to stop odors but is of course risking a wastewater leak into the floor under and around the toilet - a subtle failure that isn't detected until the surrounding floor starts to come loose.

With no signs of slow toilet drainage - flushes are normal - at this point you'd might simply defer that repair.

On 2023-03-20 by Rob

@InspectApedia Editor , I am not clear on the air/water seal point necessarily but I am certain there was no water leak at the same time sewer gas was intermittently escaping.

I know this as that toilet had water leaked previously and damaged the drywall ceiling in the basement directly below the waste pipe as it turned 90 degrees away from the toilet base directly above. We removed that drywall pending repair and the sewer smell continued, notwithstanding the toilet was resealed/reset with no additional water leakage below for a number of weeks (which I checked repeatedly over that time).

The way the air leakage was described to me was that the risers (or flange maybe?) used to set the toilet on the tile was done in such a way to be inadequate to keep the sewer smell completely contained as it should be.

It wasn’t something obvious according to the plumber who did the smoke test and repair. Perhaps it had the potential to let water out but didn’t, just by coincidence. .

On 2023-03-18 by InspectApedia Editor - "water sealed" to the waste pipe but not "air sealed"?

@Rob,

Thanks, that's interesting.

I'm not sold on smoke tests - as the leak can be in piping that is hidden in a building cavity where nobody can see the smoke. But in this case it sounds as if it worked for you.

One detail: I don't understand how a toilet base could be "water sealed" to the waste pipe but not "air sealed" - if air can leak out of a fixture so can water or wastewater. (It may not have done so simply because the drain line isn't blocked. )

On 2023-03-18 by Rob

Had a intermittent sewer smell from a remodeled bathroom installed by prior owners. The source was unclear so I had a smoke test performed before any starting on any invasive measures. We quickly found that the problem was the toilet.

It was water sealed properly but the way it was installed on the tile did not make it air sealed. Once this minor repair was made, the smell was gone. The smoke test was not cheap but it was very effective in locating the source. It also had the added peace of mind of confirming no air leaks elsewhere in the plumbing system.

On 2022-09-14 by InspectApedia-911 (mod) - keep a careful log of building activities to identify source

@Troy,

How odd. I'd start by keeping a careful log of building activities, use of mechanical systems, plumbing fixtures, drains, etc. so that you can identify what the heck is operating only at the beginning of the month that might be affecting the building drain waste vent system.

And of course step through the sewer gas sources above on this page.

Watch out: check right away for the obvious safety hazards such as a methane or LP or natural gas leak into or in the building as an explosion can be a disaster.

On 2022-09-14 by Troy

We get sewer gas smell once a month always the beginning of the month we did a smoke test that was good we added more vents still get it the smell is in the bacement

On 2022-01-06 by Inspectapedia Com Moderator - an open return air supply inlet in a crawl space is bad design

@John F,

One of the worst forced warm air heating designs possible is yours; an open return air supply inlet in a crawl space.

Most costly way to heat the occupied space

Potentially unsafe, sending any crawlspace contaminants into the occupied space

Possibly causing heater combustion air deficiency

And more.

- provide outside combustion air

- close off return air intake in the crawl area

- provide return air from the occupied space

- test & inspect for prior sewage spill or pathogens in the crawl space

On 2022-01-06 by John F

I get a sewer gas smell when taking showers or doing laundry. it comes out of the heat ducts. my air handler is in the crawlspace and the cold air return is open. in other words the air handler sucks air across the crawlspace and into the house. smell is worse in spring and fall, I have concluded that is because the air handler runs less often.

I have been fighting this problem since I bought this house 8 years ago. I have had the system smoked and scoped with a camera as well as several visual inspections, but the problem is still there.

I was wondering since it appears to be a septic gas leak in a pipe could I find the problem with an infrared camera wile running hot water through the lines. fyi the septic tank was new when I bought the house and is located about 20 feet from the house.

On 2021-10-29 by inspectapedia.com.moderator - be alert for actual plumbing drain leaks

@Jennie,

That's certainly worth trying, but

remember to be alert for actual plumbing drain leaks - wet leaks - that could lead to rot or mold problems.

On 2021-10-29 by Jennie

@Jennie, the red bucket is where the toilet is now.

On 2021-10-29 by Jennie

@inspectapedia.com.moderator, Thanks so much for the fast reply! The vent stack with the issue is one of two vents in the cabin. Since it’s a really long pipe - probably 35 feet total, we’re wondering if we could simply install something like a Studor mini-vent at the base of that vent stack, which would let air in but not out, rather than trying to figure out where the disconnect is and repair/replace it?

I’ve attached a picture of the bathroom vent - we’d put the mini-vent just above the small elbow where the ABS pipe begins. We don’t really know what the purpose of this particular vent is, other than perhaps for the shower. There’s a single sewer/septic line in the cabin and the other vent supports the kitchen sink, bathroom sink, and toilet.

The shower is on its own small offshoot as you can see in the second photo that I’ll send in a minute (shower pan is on the right side). It seems to us that the other vent would be more than sufficient to allow air into this small system, but we’d like your thoughts.

On 2021-10-29 by inspectapedia.com.moderator - Smoke tests for leaks in plumbing vent systems

@Jennie,

The observation that the strongest sewer smell is at floor gap near a vent pipe is sure an argument that a vent pipe connection was poorly made or has come apart.

If I were going to do any invasive inspecting I'd start there.

You might try renting a sewer line camera to inspect the vent pipe from its interior,
and
you might try peeping along the existing vent pipe from above with borescope inspection camera

to try to home in on the most-suspect area first. That's where you might need to cut into drywall; drywall is very easy to patch and re-paint compared with the gut renovation that would be necessary if a drain line is leaking into building walls or ceilings - found later.

Details:

Smoke tests for leaks in plumbing vent systems are in our OPINION

1. tempting to use because it's far easier to introduce smoke into a drain system than to cap off every drain opening to perform a pressure test for leaks

2. unreliable because a smoke leak into a wall or ceiling cavity is hardly likely to show up in the building interior as a visible smoke plume

3. unreliable because of the low pressure at which such tests are performed and so may indeed miss an actual leak in the vent piping

If a vent pipe were punctured by a drywall screw the odor leakage around the screw is close to beneath detection if the screw remains in place. If the screw is removed the resulting hole is usually so small, less than 1/8" diameter, (an 8-15 drywall screw has a thread diameter of 0.169" - slightly larger than 1/8" (0.125) ) that it wouldn't explain an odor complaint UNLESS the hole is in an area where not sewer gases but rather actual black-water *(toilet drainage) is leaking into a building wall or ceiling cavity.

So I'd look for the easy-to-find problems first, as described above on this page and in this article series.

Check for a loose toilet, a bad or squashed or damaged toilet wax-ring seal, for dry traps, for gurgling drain noises, etc. before going to work with a saw to cut into cavities of walls and ceilings.

Check also for leaks: water stains, or perhaps use a moisture meter or thermal camera to see if you can find any active leaks.

On 2021-10-29 by Jennie

We bought an A-frame cabin 3 years ago which has 2 floors plus an attic. It was built in mid 80s and septic system added some years later. For the past year+, we’ve been having septic odors on the second floor above the bathroom - we think from the vent pipe that runs up the wall and out the roof.

We live in a very rural area and can’t find a plumber to come out (90 mins to nearest plumber), so we’re thinking of renting equipment and doing our own smoke test.

The bathroom has been completely remodeled and dry-walled, so we’re reluctant to cut a hole in the wall. The upstairs is not completely sealed off yet, though, so there are gaps in the floor and ceiling where we installed dry-wall, but haven’t taped/mudded yet. The smell is strongest coming up from the floor gap near the vent pipe.

We’re wondering if either a bathroom drywall screw punctured the vent pipe, or if the black ABS pipe is just so old that it’s cracked or just not joined together anymore and has a gap inside. There was a dislocation where it exited the roof, and our septic guy fixed that, but he’s out of ideas now.

We have a clean-out septic trap that would be simple to send the smoke through, but my husband thinks the smoke will get absorbed by the insulation in the walls and not show up if there is a leak. Any thoughts? Should we bite the bullet and cut out the bathroom and/or upstairs wall before doing the smoke test?

We know it’s the septic because we can smell the same smell from the clean out trap and have been leaving it open to alleviate the smell inside.

On 2020-12-05 by (mod) - bathroom sewer smell sources

Rudy,

Water does not flow up into a building drain trap unless the drain itself is clogged somewhere and route. Rather water is retained in the plumbing Trap by water that is emptied into the fixture that the truck serves.

As you probably understand the purpose of that water is to block sewer gases from coming up the drain line and out of the fixture drain.

It would be no surprise that they would be drain odors if the Trap is removed and often the Trap contents and trap itself can be a bit smelly.

But if it's retaining its water sealed should not be releasing orders into the room. So the first thing to check is whether water is being siphoned out of your trap. That would tell us if there's a problem in the building venting system.

On 2020-12-05 by Rudy

The problem is a sewer smell in one bathroom.

The p trap when removed smells very bad. I clean it, replace it, and a week later the same smell is there. It is the wash basin. Why does the p trap water smell? 3 plumber's want to descale the sewer pipe and pipeline but I don't think that is the answer.

I put on a new p trap and that didn't help. House is 55 years old. Camera inspection shows cast iron wear, as expected, but that shouldn't cause water to somehow flow up into the p trap.

On 2020-11-22 - by (mod) -

Pressure test the DWV system to confirm that there's a leak;

Focus on plumbing near areas of the building where odor is strongest.

Look for signs of leaks

On 2020-11-18 by Anita

Desperate and sick house owners here! We moved into our new build house in May 2020.

There was always a slight odour in the in-law suite that we at first may be due to old boxes from storage etc. By July there were significant sewer odours in the main house and suite.

By August it was unbearable.

Most days we get a very toxic sulphur smell throughout the house. it can skip 1 - 3 days then comes back very strong. Some days the odour is slight other days are 20 out of 10. Typically will smell in the morning and again at night. Today, for example, no smell right now.

We can smell it coming thru the floor air vents and the mechanical room will often smell very bad.

It is so bad that we have to either leave the house or open all windows and doors for at least an hour. The builder can not find the problem. We have had plumbers and HVAC techs.

No solutions. Smoke test showed nothing but they are going to try again. We are slowly getting sick with nausea and headaches. Our new home insurance says nothing they can do.

We are on a septic system. Does anyone have any ideas?

On 2020-08-16 by Barb - 2019 Skyline mobile home bad smell in every room.

I bought a 2019 Skyline mobile home and their is a bad smell in every room. It does not smell like sewage but chemical smell. I thought Formaldehyde but it’s in every room.

The strange thing is I live in Florida and it is hot and humid and the smell get reall bad at night. The manufacturers sent out a plumber and did a smoke test and found leaks coming up around toilets.

They pulled toilets and put in new wax rings and caulked around them.

They changed the inside cabinet vents but I am still experiencing a bad smell.
Do you have any suggestions on what else to do? The manufacture is no help

On 2020-07-28 by Anonymous

@Todd M, that vent actually ended in the attic, so i cut a hole in roof and added the extra pipe with a rubber connector. I actually smoked it from the clean out and sure enough there was smoke in attic at connector. Roofer is coming over to redo it. He took it off to do roof.

On 2020-07-28 - by (mod) - attic sewer gas odor

Todd

Indeed we have not had a case of sewer gas increased by heat.

Are you confident that its sewer gas and not something else such as 3dead animal?

On 2020-07-27 by Todd M

The house I bought was sitting for several years. We have been dealing with a sewer smell that is worse in the summer, the hotter the worse it is.

Smell is worse in attic on the end of the house where main vent is.

The vent runs outside the house and ended in the attic, going through the soffit. I extended it to go through the roof, up about 4 ft higher then the roof.

We still get the smell.

I am wondering if the sewer smell can be absorbed by the surrounding wood and insulation.

I do plan on having a smoke test done. Curious in this particular section of this site no one else posted this type of issue in the heat.

On 2020-06-02 - by (mod) -

Gerry

You might ask the plumber if he can pressure-test the drain-waste-vent system to be sure there's no leak.

Check also for leaks at the toilet base or flange,
for improper, incomplete, or inadequate venting above the roof line

and (as I can't see context from your photo and note) review the vent termination vs. building openings, windows, doors, other air intakes, and review the vent termination: why isn't it above the roof line?

On 2020-06-02 by Gerry Savaglio

For the past three summers, we have experienced a sewer smell in the master bath coming from the wall behind the toilet.
The House was built in 2011 and smell started about three years ago.

Only in the summer months. House is located in Southern Nevada. I must state the the track of homes are located about 1/4 mile from the sewage treatment plant. Since the housing track is close to the plant, there are two sewer lift stations in the tract. Due to this, some streets have an sewer odor in the hot 105 F+ summer months.

Today a plumber ran a camera down the vent pipe behind the toilet looking for either a break or drywall screw, but found none. Looking for the next possible solution, the plumber plans to return later today and smell the wall behind the toilet, as that when the smell is the strongest. After this smell first appeared a few years ago, i was actually able to temporary plug the vent pipe at the bottom thru a clean out trap.

Since i plugged the vent line at the bottom it prevented the sewer smell from going up the vent pipe behind the wall, It does stop about 80% of the smell. I then added a temporary vent pipe via a drilled out cap for the clean out port.

This Temporary vent pipe insures proper venting in the bathroom. See attached photo. Question; What is the next best course of action to take? Plumber mentioned to cut into the wall as the camera system is very hard to see small drywall nails in the vent pipe.

Plumber also mentioned both a smoke bomb test and also to replace the toilet wax gasket. Any other comments or suggestions? Thanks-Gerry S.

On 2020-05-05 14:43:14.205835 - by (mod) -

Brenda

Try keeping an odor log: time of day, weather conditions, occupancy, and what plumbing fixtures and mechanical equipment were used or active.

That can be diagnostic.

ODOR DIAGNOSIS SIX STEPS

May also help

On 2020-05-05 by Brenda

Intermittent Egg smell in the lounge. Lasts about half hour each time. Concrete floors downstairs. Gas meter just outside window. (The gas board checked - no leak). Gas CH boiler in garage. Plumbing - upstairs bathrooms towards rear of house as us kitchen. No WC downstairs. Have no obvious external public drains - surface or sewage.

On 2020-04-08 0 - by (mod) - more tricks for tracking down a sewer odor to its source

OK. So what else can we do

Odor move through a building on air currents - and can be transported from source to other locations.

If you're sure it's a sewage type odor I remain focused on plumbing.

But first for safety can we rule out an LP gas or natural gas leak? Is there a gas supply, are there gas appliances in the home?

In addition to a careful review of the sewer gas sources listed on this page,

This companion article may also be of help

TEST FOR INDOOR SEWER GAS


Also, you could buy a combustible gas detector online and have it shipped to you.

See TIF 8800 GAS DETECTOR

On 2020-04-08 by Chelsea

Thank you. We have a plumber scheduled to come once lockdown is over, but unfortunately right now it’s not possible to have anyone come to the house.

On 2020-04-08 - by (mod) -

Adding water is a good move, though if there is a venting defect passing water through a drain can quickly siphon that water back out.
As an experiment at a basement floor drain that was suspect in a NY home I had the homeowner duct-tape down a cover over the floor drain. The odor stopped;

Odors traced to a wall are more troublesome since there could be an air leak (or even a water leak) in the vent system as it passes through building cavities. It's a bit of trouble but might be worth doing: ask a plumber to come by with her collection of expandable drain line plugs and an air pump: pressure test the drain/waste/vent piping.

On 2020-04-08 10 by Anonymous

Thank you for the reply. We’ve been adding water to the floor drain regularly, and that drain itself doesn’t usually smell. The weird thing is that the smell moves around to different parts of the house... When the basement smells we can’t pinpoint where it’s coming from.

Other times it will come from a random drain around the house, sometimes it will be a drain we are using at the time it smells so I know the trap can’t be dry, and now we are smelling it inside a bedroom wall that is shared with a shower on the other side.

Any idea what would cause this? Also, it’s usually strongest on sunny but cold days, and doesn’t smell on mild overcast days.

On 2020-04-08 - by (mod) - start by sealing the traps in floor drains

Let's start by sealing that floor drain and any other drains are traps that are suspect. You can put in water or if you want a longer-term solution you can put mineral oil into the floor drain.

On 2020-04-08 by Chelsea - strong septic odor in the walk out basement

We recently purchased a home that is about 5 years old. About 2 weeks after moving in, we started noticing a strong septic odor in the walk out basement, but couldn’t figure out where it was coming from.

We filled the floor drain with water, thinking it was a dry trap, and it seemed to go away at first but then came back. Most days it gets strong right after we take showers, and also if we run a few loads of laundry back-to-back.

(We had a plumber scheduled to come out, but before he could come, our state went into lockdown for the COVID-19 pandemic so they are unable to do non-emergency service calls right now.)

The smell comes and goes, and we’ve smelled it in various different drains around the house, on all three levels.

We thought maybe it was a clogged vent pipe, as we live in the woods and it could have leaves or something clogging it.

Today there was no smell, but this evening, the wall near a light fixture smelled so my husband removed the light fixture and the smell is coming from inside the wall now.

Any idea what it could be, and how we could fix it ourselves (at least a temporary fix until we can get a plumber here)?
Thanks

On 2019-12-05 0 - by Andrew Batson - recommends a smoke test to find vent or drain line odor leaks

I'm a home builder and have had a few cases where home owners complained about a sewer smell. The plumbers are often at a loss. But a smoke test, like with a Hurco Power Smoker quickly finds the problem by showing the leak source with a dense odorless smoke (fog). ....

On 2019-04-15 - by (mod) -

You might look in the ARTICLE INDEX and try out SMELL PATCH TEST KIT - it's an easy DIY that can track odor to a surface.

On 2019-04-15 by Pete

Hi. We are about to lose our minds. We have paid thousands of dollars to professional plumbers and nobody can find the source of the odor or what to fix. We have had a smoke test that showed nothing.

All the quick and easy fixes like toilet seals and dry traps have been done. The odor is coming from basement utility room.

We are on septic system but just had it pumped 4 years ago. Our house is only 10 years old.

The smell is inconsistent on when it comes, but mostly when washing clothes or bath tub gets drained. But it could be smell free for weeks and then be smelly for a week straight. Somebody please help.

On 2019-01-10 by JEANNE - did a smoke test and no leaks were found.

Hi, First thanks for all the great info already posted. We have had a sewer smell that comes and goes in our home for several months now. We have checked all the traps, toilet rings, a plumber changed some vents and also did a smoke test and no leaks were found.

We are at a loss, it is winter here so digging up tank isnt an option right now but there are no wet areas on wall by tank in our basement so not thinking a tank leak at the moment. HELP, can you think of any other sources that could cause this?

On 2018-11-04 - by (mod) -

Anon

Thank you very much for this helpful field report of another possible source of sulphur odors ("sewer gas odors") that we had not previously noted: a failing battery such as often found on battery-operated sump pumps and other battery backup systems.

I'll be sure to add your example to our list of sewer odor sources.

On 2018-11-04 by Anonymous

I had a plumber come to my basement because of a smell of sulfer (rotten eggs) in the basement. It was getting stronger. We tried looking at all the sewar lines, boiller, etc... He found the smell. It was the the emergency battery on our sump pump

. Either the battery was bad, or the charger was overcharging the battery. Once we removed the battery, the smell disappeared.

...

Continue reading at SEWER GAS ODOR REMEDIES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see SEWAGE ODOR SOURCE LOCATION FAQs - questions & answers posted originally on this page.

Or see these

Recommended Articles

• BACKDRAFTING & SEWER / SEPTIC ODORS
• BUILDING DRAIN ODOR SOURCES
• PLUMBING VENT BLOCKAGE ODORS
• DRAIN LINE SEWER ODORS
• DRAIN PIPING & SEWER ODORS
• DRAINFIELD ODORS, FAILURES
• FLOOR DRAIN / TRAP ODORS
• GAS DETECTION INSTRUMENTS
• INDOOR SEPTIC ODOR, OUTDOOR CAUSES
• METHANE GAS HAZARDS SEPTIC / SEWER
• METHANE GAS SOURCES
• ODOR EVENT / SOURCE LOCALIZATION LOG
• OTHER ODORS BLAMED on SEPTIC / SEWER
• OUTDOOR SEWER ODORS
• PLUMBING FIXTURE TRAPS
• PLUMBING VENT BLOCKAGE ODORS
• SEPTIC / SEWER ODOR SOURCE TABLE
• SEPTIC / SEWER PIPING LEAKS
• SEWAGE ODOR SOURCE LOCATION - home
• SEWAGE PUMP ODORS
• SEWER GAS ODORS
• SEWER GAS ODORS in COLD / WET WEATHER
• SITE WEATHER or NEIGHBOR'S SEWER ODORS
• SULPHUR & SEWER GAS SMELL SOURCES
• TESTS for SEWER GAS INDOORS
• TOILET SEAL LEAKS & ODORS
• TRACK SEPTIC ODORS to SOURCE
• TRACK SEWER ODOR by WEATHER
• TRAP SIPHONAGE & SEWER GAS
• WATER POLLUTANT SOURCES

Suggested citation for this web page

SEWAGE ODOR SOURCE LOCATION 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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