Asked on Jan 13, 2012

Why does my house smell like sewer every time it rains?

Donna R
by Donna R
Here I am again with an "old house" problem! Every time it rains hard my house smells like sewer and I am at a loss as to the cause. I put in a new sump pump, had the septic tank cleaned, and constantly check the two basement floor drains for any back-up, but nothing seems to stop the smell -- it goes away the day after the rain stops! I want to call a plumber, but would really like to have some idea as to what the problem might be before I get someone here so I can feel comfortable about what they say needs to be done. HELP!
  24 answers
  • Donna, you mention you have a septic system. Where is the location of yor leach field? It is possible that if it is in a depression of some sort then the rain water is mixing with it. Another possiblility is that the sump pump is pulling water in from the leach field after it rains.
  • Although you have cleaned the septic, installed a new sump pump. Is the soil below the house contaminated? If the old sewer pipe had failed in the past and sewage entered into the drainage system of the basement and contaminated the soil this could possibly be the reason for the smell. When the water table rises as it does with rain this could be bringing the water up enough to re-saturate the soil. When normally the water table is lower and the soil dries out and the odor goes away. I would suggest if you have an open drain system surrounding the basement floor to pour a few gallons of bleach in this area. This should disinfect the soil that is close to the surface that may be causing this odor. I would wait until the outside is dry however so the bleach will be accepted into the soil through wicking action. Doing it now when ground is wet will only dilute the bleach and may also carry it away through the drainage system. Thus making it worthless to do. This all sort of works like a skunk smell. Goes away when the weather dries up, but as soon as its damp it comes back. Trust me on this I have first hand knowledge of smells such as this returning.
    • See 1 previous
    • Jay Peralta Jay Peralta on Jul 25, 2017

      I forget to mention that the house has a septic tank and the remodeled bath is the closest one to the tank.

  • Julia M Julia M on Jan 17, 2012
    I had a very similar issue in an old house a few years ago - long story short, it ended up being a corroded leaking old sewer main line directly under the kitchen floor which was torn up by the next owner and discovered! While I was there and had the smell, everything was working fine, nothing leaking in the house anywhere, just the sewer smell. awful.
  • Southern Trillium LLC Southern Trillium LLC on Jan 17, 2012
    Woodbridge gives some great points. We helped a friend several years ago who was experiencing similar problems. The lady had just had all new field lines installed. Then she began noticing a sewage smell every time it rained. There was a working sump pump in the crawl space under the house and it pumped a lot of water out during and after a rainfall event. I will try to make a long story short, but it is hard to shorten a 3 year chain of events. The septic field line installer was the best in the area. He came back out and said that maybe the filter on the outlet of the tank was clogged, only way to know would be to open the tank. We took our backhoe over, lifted the lid, only to find the tank full to the rim, but no filter in the tank, so no clog. Took the backhoe out, and began digging between 2 runs of the field lines. The hole began to fill with water that smelled of sewage. Next came a soil engineer who came out and sampled the property, stated that the periodic water table is too high, and is flooding the field lines. Thus, the tank backs up, excess water seeps out around the lid on the tank. This contaminates the soil between the tank and house. What used to be groundwater getting in the crawl space is now water carrying effluent water, thus the smell appears in her house. A simple fix to help her during this whole time was an attic fan mounted in the door of the crawl space. With a simple remote control plugged inline, she could turn the fan on before rain, and turn it off after a period of time following the end of the rain. The soil engineer recommended re-grading the backyard to help direct all rainwater from the house, because no other location on her property was clear to move the field lines. The county officials were brought up to speed. They would not allow a shallow pump system. The sewer system is ~1,000 feet down the road at the next intersection, but no plans were in place to bring the line their direction. She and her neighbors all have problems with their septic systems. The only fix that has worked was to have the foundation exposed and fully waterproofed with a weeping tile installed to carry the water away from her foundation. That has solved the smell issue for her, but obviously does not fix the septic field and high water table issue. Hopefully the county will make a change and run sewer up the street. Let's hope your situation is not this severe.
  • Terry & Maureen Terry & Maureen on Aug 21, 2013
    Ok, here's one for the books: never had the problem till we moved to the country. Had a new septic system put in, and since then we have a stench every time it rains hard. +A lot of water pooling under the house (manufactured home). Dug it out and closed off all the leaks, sealed and secured. Shower will have to be replaced, but not causing any significant problem. Found 3 under sink drains that were either loose, no maintenence valve or just needed to be tightened. Washer lines all cleared, same for water softner and water heater. Had a new A/C put in and they drained it under the house, so they turned it around and now drains into the cornfield. Drain specialist came today and did the peppermint test - walla! found the source - drain under the bathroom sink had a "$6 mechanical vent - not the $20 vent" - in other words, it was out of code and couldn't do its job, so he capped it and when it rains again, it will either stink in the next sink drain or we won't smell anything. If we don't smell, cap stays, if it stinks, we buy the code vent. Ya gotta love it :-)
  • Rockin Ronnie Rockin Ronnie on Feb 21, 2014
    Just seal off the sump pit. I had the septic leach issue and this works for now. Sewers coming in 2 years so I can wait. Great house and property .. worth it.
  • Erin Long Erin Long on Apr 14, 2014
    I am having this problem. My landord has been out and dug up the septic tank to reveal that it was leaking. He had it repaired but the smell still remains. Is this smell toxic for my family?
  • Cheryl Waltman-Navarrete Cheryl Waltman-Navarrete on Nov 04, 2014
    I live in an apt with a dirt filled backyard. It finally rained the other night and now it smells bad in backyard what should I do?
    • @Cheryl Waltman-Navarrete just sent you a quick hint on asking questions that you will find useful To answer your question. That smell is money to farmers, however there is little you can do to stop the odors from the fresh organic makeup of the soil. If its an abandoned property that has the soil, contact the township. If its the landlord fixing the yard, with new landscaping etc. wait it out. If its simply the way it has been for a long time, depending upon your landlord, you could request that he does something like put grass down or simply move. Unless he is violating some sort of local township law he is under no obligation to do anything. As a tenant there is not much you can do unless its a health issue such as excessive doggie droppings etc.
  • Rachel Rachel on Dec 17, 2014
    Water building up in the soil causing the bad smell makes sense but how can I find out for sure where the smell is coming from. If it's the soil then how do I know for sure where to dump the bleach? It's not exactly super cheap to buy s lot of bleach and I worry that it may not be good for animals. What about plants? I have an idea for where I could start at but I need more information. I have two bathroom no leaks or clogged drains. If someone fixed a leak prior to my moving in the soil contamination makes sense. Only one bathroom smells bad and it smells bad in the vent. Does anyone care to comment on this problem. Obviously I need to wait until the soil is dry so I do have time.
  • Shirley McElmurray Shirley McElmurray on Apr 16, 2015
    I don't have a septic tank, but, have that awful sewer smell in the house. Could it be from using drano and have it setting in the sink till it goes down?
  • Stevo1025 Stevo1025 on Apr 18, 2015
    I have been experiencing this same issue and don't have a septic tank. It seems to come from the A/C registers in the ceiling, but only certain ones. I don't know who to call...plumber, HVAC, General Contractor? The smell is very foul and only started this year after a hard rain. We were told that it could be from a drain that doesn't get used much and tried pouring bleach down it to flush through periodically. They thought it could be back flowing through the p-trap and causing the foul odor. That didn't fix it. I'm out of ideas and wonder how extensive this search and remedy will be...
    • See 4 previous
    • Aaron Aaron on Aug 04, 2020

      Did you ever figure it out? Sounds like our problem.

  • Barb Chapman Barb Chapman on Aug 14, 2015
    You don't necessarily need bleach. If it's a p-trap that has dried out from non-use, you just need to run water down that drain for a while (maybe 5 minutes depending on the faucet tap) every 6 months or so. (Play it by ear - it depends on the size of the pipe.) A dried-out trap allows the sewer gas to come through; it's not the same as a back-flow of actual sewage.
  • Debra R Fisher Dailey Debra R Fisher Dailey on Oct 03, 2015
    When it rains it smells like septic in my house
  • Jud4612961 Jud4612961 on Feb 15, 2016
    I have a septic smell every time it rains
  • Kimberly Buchanan Kimberly Buchanan on May 01, 2017

    We have a septic smell everytime it rains hard in our house it's so awful I read online to run water when this happens and it does eventually push the smell back out of the house bit I have noticed in the very back of our yard where I'm assuming field lines are when washing clothes etc there is bubbling in the ground and even on dry days the ground in that spot remains wet and the grass is greener I need help as to what to do as we are about to buy this house and my landlord hasn't dome anything about this problem as of yet..

    • Ellis Ellis on Jan 12, 2019

      Bubbling in the ground is not a good sign. Get an inspection of your septic system BEFORE you buy the house. You may need major septic work done, and it can be very expensive. Your landlord should fix this now, but if he won't, the cost of fixing it should come off the purchase price.

  • Heather Dean Nelson Heather Dean Nelson on May 31, 2017

    Ok we had that problem one thing to help is be sure the roof vents are clean. We eventually had our entire septic moved from to deep in back to front yard we are close to

    lake so water issues are possible we discovered our main issue was crack in septic tank lid allowing rain water in filling lines pushing gas into house but not fluids that's the theory. Putting new wax rings on toilets as well. When gas starts we found out pour baking soda over all drain openings sinks tubs shower and then when past flush it w vinegar it will have added bonus of cleaning pipes but the soda will absorb block that and help a lot

  • John Macphail John Macphail on Sep 11, 2018

    Please Help:

    We bought a new built house in August of 2015. We started noticing the rotten egg/ sewage smell whenever it rained heavily. The smell is coming from sump pump area not the drain. We have confirmed, It’s not city line water coming into the house. We have changed the sump pump a few times. What could it be. Is one of the drain leeking onto weeping tiles? Or did builder forget to connect sewage pipe?

  • Jody Stewart Jody Stewart on Nov 05, 2018

    We have this problem and the smell is very overwhelming and makes it hard to sleep cause if the smell. As a matter of fact it’s doing it right now and it is bad

    • Ellis Ellis on Jan 12, 2019

      If the smell is very overwhelming, you may have sewer gas leaking into your home, perhaps through a drain pipe. This is not good for your health. Have a licensed plumber investigate this problem ASAP.

  • Amy Amy on Jan 12, 2019

    We do not have a septic tank, and we are having this problem. But it started with a long, loud sound that lasted a couple minutes. After looking around it seemed to be coming from the toilet in the basement. About a minute later, the smell started... Any ideas?

  • Mary Ann Iyoob Mary Ann Iyoob on Feb 13, 2020

    Is this smell toxic for my family

  • Mary Ann Iyoob Mary Ann Iyoob on Feb 13, 2020

    Is this smell toxic for my family

    • See 1 previous
    • Kaan Kaan on Apr 17, 2020

      The septic smell is essentially methane gas so yes at high concentrations it is not healthy. I am not a scientist so don’t know when it is an actual threat but it is not safe at some point.

  • Polly Polly on Feb 26, 2020

    you might try pouring a little bleach In the basement drains to help the smell but you should have a plumber check it out I think I remember a friend having this problem and the plumber did something to have a little water to drip in the drain all the time . Now I'm not sure what they did but whatever it was it fixed it

  • Judith Judith on Apr 17, 2020

    I have a friend that used to have this problem, only her basement was below the water line, a mile from a chemical waste dump ! She was able to sell her house to someone who visited only on the days when there wasn't a stinky (or colorful) problem. Perhaps you should consider that....