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Sewer Gas Smell

DEAR TIM: My daughter's house has a chronic sewer gas odor problem. The odor is strong when it rains and the furnace or air conditioner is operating. The odor gets so bad my daughter and her family evacuate the house. Three plumbers have not been able to solve the problem and we have checked all plumbing fixture traps, caulked where the basement floor meets the foundation, etc. My daughter is ready to sell the house for a loss. Can you help? Dave S., Shelby Township., MI

DEAR DAVE: Sewer gas can be a vexing problem to solve, but it is by no means impossible. As much as I hate to say it, the three plumbers that were consulted are either inexperienced or they do not keep up with technology. The good news is I doubt your daughter has to move and take a loss. It is my guess the source of the odor can be found and repaired for less than what a moving company would charge just to move your daughter and her family.

The water seal in this toilet is broken. The water level has dropped below the back lip of the trap and sewer gas was entering the room as I took the photo. PHOTO BY: Tim Carter

The water seal in this toilet is broken. The water level has dropped below the back lip of the trap and sewer gas was entering the room as I took the photo. PHOTO BY: Tim Carter

Sewer gas is created by the decomposition of waste materials that are found in public and private sewer systems and private septic systems. The characteristic odor can be overpowering and it is toxic. To add further insult to injury, the gas is explosive as it often has a methane component.

Plumbing drainage systems are designed to keep this sewer gas inside the pipes and any that does exit to the atmosphere happens outside the home through the vent pipes that poke up through the roofs of houses. These vent pipes on the roof are actually intake vents, not exhaust vents as most people believe. When a large volume of water enters a plumbing drain pipe it pushes air in front of it towards the sewer or septic tank. This air must be replaced and it is sucked into the plumbing system through the roof vents.

The source of the sewer gas can be plumbing fixtures whose traps have gone dry or have lost enough water that the water seal within the trap has broken. You would be surprised to discover that water can rapidly evaporate from toilets and the traps below tubs, floor drains and just about any fixture within a few months. In fact when my daughter is away at college I have to flush the toilet in her bathroom every three weeks to keep the bowl filled with water. If I don't keep the toilet seat down, I have to flush the toilet weekly as some household pets seem to love to drink water from clean toilet bowls.

Cracks in either plumbing drain lines or vents pipes are the other source of sewer gas leaks. If the crack is in a drain line, you often see an associated water leak. But vent pipe cracks are far more elusive. They can leak vast amounts of sewer gas and you might not be able to locate the source easily without a special machine. The furnace and air conditioner clue tells me the leak might be in a vent pipe that is close to a return air duct. The leaking sewer gas is being sucked into the return air system and then broadcast throughout the entire house by the air handler in the furnace.

Sewer gas leaks can be quickly discovered by a plumber who owns a very cool machine that generates artificial smoke. The smoke is simply visual and does not create a lasting odor nor does it stain any surfaces in a house. The plumber connects the smoke generation machine to the plumbing drain system and then blocks off the drain pipe leading to the sewer and caps off all roof vent pipes.

Once the smoke machine starts, it begins to slightly pressurize the plumbing system. If there is a cracked pipe or a fitting joint that is loose, the smoke readily exits at that point before it would bubble up through a fixture trap filled with water. Usually the source of the sewer gas leak can be discovered in less than one hour.

Sewer gas problems can also be caused by plumbing vent pipes that are clogged. This can happen in old homes where a cast iron vent pipe gets clogged by years of rust scale that falls off the inside of the pipe and clogs a 90 degree bend in the pipe.

Tennis balls, leaves, and all sorts of other debris can clog plumbing vent pipes. When a vent pipe is clogged, the replacement air needed by the system will get sucked into the pipes through a fixture inside the house. When a large amount of water is placed into the drain pipes by a toilet or a powerful washing machine pump, it can readily suck the water out of a nearby bath tub trap or even a kitchen sink trap. Once this happens, sewer gas immediately enters the room through the dry fixture trap.

To slow evaporation from fixture traps that are not used on a frequent basis, fill them with water and then slowly pour four ounces of mineral oil into the fixture or floor drain. This mineral oil will evaporate far more slowly than water and the trap will remain wet for many months.


Author's Notes:

I received these emails after my column was printed.

"Tim:

In regard to the sewer odor problem in Shelby township Michigan: If they have a sump pump in the basement and have a french drain around the perimeter of the house, there could very easily be a broken sewer pipe right outside the basement wall. When it rains, tainted water gets in the drain, goes to the sump, odor is in basement, return air to the furnace distributes odor throughout house.

Enjoy your column in the Telegraph Herald."

Dave B., Dyersville


"Hi Tim:

My name is Gary Whiteman of Whiteman Land Service, Curtice, OH. We do pond construction and new home site development.

I read your article in the Toledo Blade, Dec. 18 and noticed that there was no mention of possible sewer gas from homes that have a leach field system. We have had many people complain of sewer gases from their basements. We have found that the cause was due to other contractors who did not remove previous farm drainage tile from under the leach field area and to the home foundation or basement.

Thus, the waste water travels through the farm tile under the leach bed to the drainage tile around the footer and into the sump crock inside the basement. To solve this would be to remove the farm tile between the leachfield and home.

Contractors excavating for the basement or foundation, and also the leach field, should remove these tiles at least twenty-five to thirty feet away from the home area. I hope this info will be helpful.

Regards,"

Gary


"Dear Tim,

We had a perplexing sewer gas odor in our home. After spending over $3,000 in fees with plumbers, locators and other experts, we still had no answer.

Finally a very knowledgeable plumber discovered an illegal connection in our drain system. The person who installed the condensate drain line from our air conditioner installed it without a vent line. Each time our washing machine would pump water into the drain system, the rush of water would siphon out the water in the small trap of the condensate line.

The sewer gas from the main sewer line would then travel up through the condensate line and into the actual air conditioning air handler. When the air conditioner would run, the moving air would suck vast amounts of sewer gas into the ducts and broadcast it through all of the air vents in our home.

Once the condensate line was disconnected from the drain line and piped directly outdoors, our sewer odor disappeared immediately."

Sandra Farmer, Paradise Valley, AZ

Column 599

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54 Responses to Sewer Gas Smell

  1. Hi,
    4 years ago we had a new septic field put in, the tank was not replaced, 3 business advised the tank was fine. We have noticed a terrible septic gas smell outside of our home. Water drains fine, no back ups and no smell inside the house, just outside. So who do I call? Do I call a plumber or septic company?

    Thank you
    Jamie

    • Jamie, did you ever resolve this situation? Sounds just like mine, only the whole system was replaced. The installing company just says to add more rid-x. The old system did not stink, but was condemned by the county. Nothing changed with the inside plumbing. thanks, I'm going crazy.
      Charlene

  2. I have read the problems about sewer gas and have a unique situation. We moved into a new home and when we leave the doors open to the back screened in porch we get what smells like a sewer gas odor in the house. there is a sewer pump station within about 50 yards behind the home but the is downwind of the house. I sit on the back porch frequently at different hours of the day and there never seems to be a smell outside. The smell is only inside after the doors have been opened for awhile. Research to date has been for naught.
    Any suggestions would be appreciated

    • This may not be your problem, but my sunroom had a terrible sewer smell when I left the doors open. Seems as though pet urine was the problem. Even after it was cleaned, it remained in the grout. I have since covered the tile with linoleum and the problem is gone. You may check to see if the former owners had pets.

    • I just came across this while I was searching for an answer to the same exact problem. We recently had extensive plumbing work done due to a flood in the house and since we have moved back in are dealing with this. Ive had a couple of plumbers come by and they all seem to think I'm crazy and have not been able to help at all. I would love any advice you can give

  3. I live in a Condo and called the association to report the sewer gas in by unit. All they did was to tell me to call a plumber. I am retaired and can not spend a lot of money on a plumber. It has been almost two weeks now and it effects my eyes.
    What should I do? I live in Aurora, Colorado, at Foxdale.
    Carolyn

  4. Hello;
    I had a sewer smell in bath tub until I had trap replaced. now I have sewer smell in wall where vent pipes are located. The smell only comes when the temperature outside in 85 degrees or greater.

      • I have this same problem with a sewer smell in the master bathroom only when the temperature outside in 85 degrees or greater and the A/C is turned off. (It is not noticeable when A/C is on.) I have an unfinished basement with bathroom pipes exposed, and I put a pvc sealant on every visible pipe fitting and connector. Also checked the caps on the clean-out and it was tight. House was finished 11/19/07. While house was still under warranty, the builder had his foreman come by to check it, and they found nothing wrong. The master bath wall has never been finished (the builder dropped the ball and didn't tile it. Could the problem be a leak in a pipe inside the wall? They seem to have used a lot of scrap pipes on my house and there are connector fittings every 4' to 7' from basement floor to roofline.

  5. We have noticed a septic smell from our septic system had it pumped out still from time to time we would smell it outdoors, have added enzymes for the bacteria, still have the problem not all the time, found a place in the yard where the smell is on the ground but the ground is not soggy. The only drain we have an issue with is the washing machine will back up into the kitchen sink when it spins out, but it drains on down. Really need help on this.
    Thank you
    Dena

    • Dena, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

    • Kim, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  6. I am a new City Maintenance personnel. I have inherited a problem with one of our buildings that has a sewer gas smell ONLY when there is a northwest wind. It is a flat roof building that slopes from east to west, shares walls with two other buildings and it is actually shorter than both adjacent buildings by about 10 feet on the north side and about 30 feet on the side south. The sewer piping is new with no cracks. The vent pipe has a frost-free cap which is about 2 feet from the top of the roof. The closest shared wall to the pipe rises about 2 feet above the pipe about 8 foot away to the south.

    • David, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  7. The toilet in the master bedroom appears to not have been flushed when we return home from work and has a strong odor. It looks as if the sewer is backing up but the plumber could not find any blockage. Any ideas?

  8. I also have a sewer gas smell, have investigated the p-traps, poured bleach, it does seem to be when the blower kicks in on the furnace so I'm thinking it's the vent pipe. I also have arranged to have my septic tank pumped just in case that is too full and not working properly. Any other thoughts?

  9. Our home is built on a slab. We are experiencing heavy sewer gas odors. We have had two plumbers check it. The first one replaced a drain the second one repaired a toilet seal. The odor is still very bad . It is worse in cold weather. What else do you recommend ?

  10. My problem is sewer gas outside my home. We have city hookup. My general contractor did his own plumbing? Anyway when it was time to hook up to the city sewer line he discovered that one of the supports for my deck was directly in the way. Instead of a nice straight outlet from our house it's crooked and I'm thinking that it does not drain our home correctly. I think that this creates an usually strong oder from a slow moving system. So I think a lot of gas is coming of the roof? Any comments.

  11. Hello,
    My family and I live in a 1949 Cape Cod style home that has a horrible sewer gas issue. Not every time but when you flush our toilet upstairs the sink and tub gurgle and then put out sewer gas smells. We have had a local company come to our home. They checked all the traps in tub, sinks, basement, and also checked the roof vent and outside municipal tank. The cleaned the traps and checked the flow into the tank outside. They were at a loss to what was exactly the problem. The man told me it could be that the house isn't properly vented or that the older pipes could need to be replaced. We have no clue and I would like to have an idea of what it might be so we can try to remedy this.

  12. We have a suspected sewer smell, however none of the P traps are dry. From the sink the waste pipe flows almost horizontal to the right and then vertically straight down through a spare room one floor underneath, then into the floor of the spare room and turning horizontal and exiting with the rest of the plumbing. We have had the waste pipe inspected with a camera and a smoke machine. There are no visible defects. There is no ventilation for this waste pipe. However each plumber who looked said that there should be a vent, but if it was a ventilation problem the smell should be coming from the sink upstairs through the trap. Is it possible for the smell to seep through the PVC pipe and into the room? This pipe is waterproof and the smoke machine found no leaks. It's a bit perplexing. The smell is only noticeable when the window and door are closed for more than 2 days.

  13. I have been gettn a wif of rotten eggs in & around my home for 6mnths both me my neighbor have been complaining to my landlord since i moved in 6mnths ago he dint smell what i was talkn bout so hasnt taken it seriously...mean time over the past 6mnths ive gone 2the hospital & drs complaining of headaches dizzyness neuseu & major fatigue without any help frm them cuz every1 wrote it off as my disability so i thot mayb i was losing it....but i was gone 1day for a long time & came home & my house smelt worse not rotten eggs this time like human increments i called over my neighors & we sniffed tell we located the source its a pipe in my food pantry thats suppose 2go up 2my ceiling but its missing a whole piece of pipe so sewege gas has been leaking in my house for 6mnths im calling my landlord now & sure he'll fix it promptly but is this sumthn i should go see a dr for or is 1s fixed no longer somthn i have 2worry about im just concerned since ive been sick a long time

  14. I had this problem in my new house - it ended up being because of my high speed Bosch washing machine. The spinner was set on 1200, and it dried out the nearby traps, letting up sewer gas, which was spread around the whole house when we had the furnace going. I was almost ready to move out, but after spending days doing research online, I reset the spinning down to 600-800. The smell was gone, and the clothes were spun just fine. Such a simple solution.

  15. help I have a house that is now 4 years old when I bought it there was a terrible sewage smell everytime it rain I have tried filling all traps wth water and bleach with no difference it is a three level house with a grinder pump in the basement and the smell seems to be worst on the ground level floor my drain field is down hill of my house approximate 100 ft

  16. Hi,

    We are in an apartment and something is wrong with the central air conditioning unit or the sewer pipe that it drains into. Maitainance (sp) have been over to clean the drain pan, coils, and pipes that go into the sewer, but when the air conditioner has ran for a while and stops intermittently the smell starts. No smell really coming from the air ducts, just around the unit when it intermittently shuts off. It is hard to decipher where the smell is coming from, except maybe the drain pan, drain lines. The furnace does not smell in the winter, when the air conditioner is not running, so this seems to rule out a dry sewer trap. Actually, maitainence came over today and ran water down the sewer drain, it was better, but now the smell is back. Any suggestions?

  17. What if the smell is coming out of the fawcett itself. About 2 years ago I had a rotten smell when I flushed my bedroom toliet. Not all the time, just enough to know when it stunk. Then it went away until about a month ago. Now it happens in my shower and bathroom sink. If I let it run for a couple of minutes it will happen until it "runs out" of stink. Then water is normal again. Is this the same as sewer gasses when it comes out of the spigots and shower heads? And what should I do?

  18. we have a leech bed. the washer waste collects there. it is two 50 gallon drums with drilled holes. it has filled up over the four years. it smells when we wash. what can we do?

  19. Dear Tim,
    We recently demolished an upstairs bathroom. I now detect a sewer odor in only certain areas of our home (especially the adjoining room which has the return vents in it). The demo'd bathroom has no odor and toilet drain has a rag in it so we wouldn't have that problem. We are waiting for our contractor to begin the remodel, but in the meantime, how do we figure out where the odor is coming from? Is there a chance that a pipe was cracked during the removal of the tub? Thank you in advance for your help/advice.

  20. I get a terrible sewer smell in my house when I do anything that requires running water such as the shower or washing machine. This only seems to be a problem when the temperature drops below 40 degrees. I have had the sewer tank pumped and the sump pump replaced but it still happens. HELP

  21. Where do you live- can you come TX to help us?! We own a property that was built in the 40's and cannot seem to find the solution, we've been told by tenants that the former owner did a smoke test but never found anything- i brought in the people that did the smoke test and "he can't remember" we had a plumber we trust cap off any open lines, foam any open areas replace a broken toilet all in the properties basement. I get calls nonstop from tenants and although we want to help, no one seems to find the solution!

  22. Hi, I have a brand new trailer on a gravel pad only. However someone did have a different trailer on this lot before. I get a horrible egg smell coming from the heat vents(in winter) and also from under the deck year round. From naked eye inspection, I have no busted pipes. I share a septic with other trailers in the park. I have a low water level in the toilets but otherwise no drainage issues. Please help!

  23. After owning our home for 2 years we started smelling sewer gas in our bed room and our office the smell was very over whelming. All the these rooms are next too the second floor bathroom. I did a lot of reading and performed all the suggestions. I changed the toilets wax ring and all the drains had water. But after this the smell was still there. I took off the toilet bowl again and opened up the wall next to the toilet to take a look at the plumbing. The house is old but the plumbing was all up dated with PVC. I flushed the vent with a hose. The smell has decreased but we still catch wiffs of gas here and there. I was wondering if the piping under the sink was my culprit? It's not leaking water but can gas escape through poor seals?

    Thanks
    Michael

  24. We seem to have sewer gas in the whole middle level of our house. It does not really smell in the basement or upstairs. My bathroom had a strong sewer smell under the sink without a plumber my husband duct taped the fittings the smell is better but not gone and a vent pipe is located in the wall behind this sink. Also on the opposite side of the house quite some distance it also smells like sewer gas in our laundry room. I've been so ill since the gas smell. I called in sick for work for a week I didn't know these gases could get you sick.

    • Yes, I do make house calls. It's pretty expensive to get me to come from New Hampshire. Click the SHOP icon at the top of the page and then look for the Consult Tim text link.

  25. The sewer gas smell went away. We had a plumber check the pipes with smoke bombs and he said none came out anywhere. We also had our tank pumped out. Now after losing electric for 24 hours after a storm( we are all electric) first the basement was terrible with a strong sewer gas smell and now after the power came back on the sewer gas is smelling in the same places as it was before. We have our washing machine in the basement and it drain in our sumo pump. Can you think of any reading this is happening? Please help

  26. By the way the smell now is gone from the basement. It's just in the middle section in our house. In certain areas you can smell the odor. The smell isn't in one side of the house it is separated quite a distance

  27. Sewer gas smell when blower comes on for heat or AC .
    Only smells in master bath and adjoining dressing area.
    Had a couple of plumbers who could not find the problem.
    Any suggestions?
    This is a doublewide mobile home (2 years old) and I am on an aerated sewer system.

    • Type BIOFILM into my search engine here at AsktheBuilder.com. Assuming the plumbers VERIFIED your toilet gasket is fine, the odor could be coming from your sink and shower drain tailpieces.

  28. Hi, hoping you can help. We bought a house in May and still can not move in due to a terrible smell in the master bedroom and bath. We have had the septic tank cleaned and the pipes are clear plus traps. But every time we run water in the bathroom this smell comes into the bedroom, the wall the smell is the worst there is no plumbing per the crawl space. So we are stumped please help!
    cindy

  29. Hi, appreciate your expertise and knowledge for plumming problem....washed a load of clothes (medium size), laundry room or kitchen sink no back up of water. But, the back to back bathroom tubs and toilets backed up and won't drain. I have plunshed but to no avail.
    Nothing overflowed, but I have noticed water behind and around toilet and baseboards in the first bathroom. and water is much much lower in masterbath toilet and tub adjacent to first bath...being back to back i am assuming pipes are connected to each other and septic tank is in front yard. reading other answers...I'm thinking maybe something is clogged ...can you help?

    • You have a clog..... Hire a pro to clear it. BEFORE he leaves the house, have a helper TEST that the clog is gone. Have two five-gallon buckets of water in both bathrooms. At the SAME TIME pour as fast as you can both buckets of water into the toilet bowls. See what happens. If there is NO CLOG, the drain line will handle that much water without the toilets overflowing.

  30. Hi Tim, we moved into a 30 year old home a couple months ago. We have since discovered all kinds of plumbing issues and have had most all the plumbing under the house replaced. What lead to the discovery of all the cracks and leaks was the horrible odor coming from the bathroom. After replacing all the pipes the odor started to go away. We are adding a bathroom at the other side of the house. They completed it this week and set the new toilet. When they opened the flap to set the new toilet, the odor came back. Even after setting the new toilet the odor is horrific and now it is back in the old bathroom where it started. Any ideas Tim?

    • My idea is that I'd want to know if the seal under both toilets IS really sealed......

      I'm about to do a comprehensive video showing how critical the placement of the toilet flange is to the finished floor surface. There's VERY LITTLE margin of error.

      What's more, if the toilet was NOT INSTALLED correctly as they were setting it, that can RUIN the seal. Setting a toilet is an art. It's not as easy as it looks on all those HGTV shows. I've been a master plumber for 35 years and know a thing or two about toilets.

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