Rancid smell after inside main sewer line replacement... not sewage.

by Matt


So a long story short, we had old cast iron for a main drain pipe in our basement start leaking at the trap. We had a plumber come in, and he replaced all of the cast pipes with PVC. During the replacement, there was an obvious smell of sewage, but also whatever smells the pipes held inside them (I think) mainly from whatever water spilled on the floor.

Its been nearly a week, and the smell of the pipes are still inside our home. It is definitely NOT a sewage smell.

Heres the deal; we cleaned that floor with bleach, and ammonia at 2 different times. We have left windows open all day, with fans blowing out. We’ve sprayed many different things in the air, and on all surfaces. Due to a really humid couple of weeks, we even have left the a/c’s on during the day to try and keep the air dry, thinking it might help get rid of the odor. The basement where the pipes were actually doesn’t smell nearly as much as our top floor.

Is this just due to the ridiculous humidity we are experiencing? What can we due to get rid of this smell?

Any advice is appreciated.


  5 answers
  • Oliva Oliva on Aug 09, 2018

    Hi, Matt,

    It's possible that your plumber missed some miniscule cracks in the piping, which have since expanded or collaped. It could be that adjacent pipes sustained damaged, but were not noticed, when the work was done.

    Try putting 2 cups baking soda and 2 cups distilled white vinegar in each drain. Wait 45 minutes and follow with 2-4 quarts of boiling water. Do this for all the drains in your house, startinng with the basement/garage, and continuing to upper levels of the house.

    Remove all sink plungers and check for hair/grease/soap residue, which may be black and slimy (requiring 20 or more Q-Tips to remove what you can access). Repeat the baking soda routine once more, if needed (more black slime may surface). If the problem continues, call the plumber back, because another hairline crack may be lurking elsewhere.

    Repeat the baking soda routine monthly, switch to hard milled soaps without fatty additives, or use thinner liquid soaps and hair traps at all drains.

    I wish you luck, having experienced something similar...

    • Matt Matt on Aug 09, 2018

      Hello Oliva,

      Thank you for responding.

      I have really done what i can to inspect the work the plumber did. I am not a plumber, but have some knowledge of the system. Obviously, hairline cracks are difficult to spot. However, on a less technical note, i have been really putting my nose to work, and have continually smelled around the pipes (which are fairly accessible) and really don't smell anything around the pipes. Just to be sure, the 2nd day, i actually washed all of the pipes with bleach and water.

      I will try your treatment for the drains, but i have also smelled every drain in the house, and it doesn't seem to be coming from there. But if the vinegar smell becomes a lingering smell (like this current smell) at least i may know there is in fact a small crack somewhere.

      This is an old house (1864) and i am sure its very possible for the smell from the basement to make it to the top floor. I am (in a way) hoping its just trapped, or we missed cleaning something. But man, what a unique, gross, rancid smell!! I've had septic work, and sewage smells before, but those pipes were just awful! lol

      Thanks again,


  • Pat - Australia Pat - Australia on Aug 09, 2018

    Hi Matt....I would think your basement is concrete. Yes the humidity has caused this. I would consider to now: If you have carpet on the top floor, it will need to be professionally dry cleaned...Not cleaned with water..But dry cleaned. It may help what is trapped, in the carpet.

    • See 1 previous
    • Pat - Australia Pat - Australia on Aug 09, 2018

      Matt...l have been thinking and l know carpet very well. .if you can get very close to the carpet..smell it and if it is bad then it may have been trapped. I can not tell you how bad carpet can be for trapping smells. Not just for a short time!..lf it stays it may have to be taken up. Carpet is not one of the best floor coverings that we can have...sadly.

  • Kauai Breeze Kauai Breeze on Aug 09, 2018

    Could there be something stored in your attic creating the smell, i.e. Christmas candles and decorations? With the extreme heat things melt and give off fumes. Check it out - there could even be a dead animal up there. It could just be a coincidence that the plumbing repair and high heat happened at the same time.

    • Matt Matt on Aug 09, 2018

      Hello Kauai,

      I thought about the attic, and actually did pull down the stairs and popped my head up there. It was about 300 degrees, but didn't smell at all up there. There is a couple of vents up there too.

      But i lived in an in-law apartment that was prone to mice and field rats, and have had plenty of them die in the walls. I remember that smell too, and this smell is very different.

      Thank you for responding.


  • Sharon Sharon on Aug 22, 2018

    First I would call the plumber back and get his opinion why his job still stinks. Then I woud buy some Room Shocker from Biocide Systems -get a 4 pack and set one or two off on each floor. You can get on Amazon, Lowes, Home Depot and Walmart.

  • Matt Matt on Aug 22, 2018

    Sorry for the delayed response, but I’ve (with help of a lot of people) finally solved the problem.

    Basically, we started off with just the gross smell of the old pipes, but last week we started getting an actual methane smell in the house, which started out as a slight smell, then turned into being constantly strong.

    The bathroom was moved long before we purchased the house. But the smell was coming from the old bathrooms location. When the bathroom was moved, they didn’t remove the old drain pipes, and just capped them off. So in theory, the old pipes turned into a 2nd (unnecessary) ventilation. After talking with the plumber, he believes that the people who moved the bathroom either didn’t cap off the pipes correctly, or there is damage somewhere that no one can see. And because we removed the damaged trap (which was leaking, and the original reason for the repair) and replaced it with a standard “straight” drain, the sewer gas was making its way back up the pipes, and out of the hole (where ever it is) instead of out the roof like it’s supposed to. So he suggested capping the bottom, and the top (on the roof) of the now useless pipe. So I did. Within hours, the smell dissipated, and now is 99% gone. So that’s fantastic.

    Only thing that is a problem now, is that our kitchen sink “burps” more, and is not moving as quickly. The rest of the drains seem fine, including the toilet, tub, and bathroom sink. I may have to add a vent to the kitchen sink to stop it from burping, but I’ll take that over the smell any day of the week.