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Thread: Rotten Egg smell when washer runs

  1. #1
    DIY Junior Member resolaru's Avatar
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    Default Rotten Egg smell when washer runs

    Over the past year or so, we have noticed a rotten egg (sewer) smell in our laundry area when the washing machine is running or has run. We have a Fridgidaire side loader that we purchased new about 4 years ago. We never had a problem with it making a smell in the first 3 years. I'm 99% sure the smell is coming from the discharge line and not the washer itself.

    About 3 months ago, I physically moved the dishcharge line 2 feet closer to the main stack, thinking that it was not close enough to the stack for venting (see attached pic). You can see in the photo where the old line was from the paint marks. The discharge line goes into a drum trap. I use the correct discharge hose from the washer, with the curved piece to go into the PVC discharge pipe. The problem seemed to disappear for about 3 months after I moved the pipe. However, we started noticing the smell again this past weekend.

    Name:  Washer-discharge.jpg
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    What could be causing this smell? I'm guessing that mold/algae or something is growing in the drum trap and causing this smell. Why would it do that? Is there anything I can do to prevent it or something I can do to neutralize the odor? We only smell it when the washer runs or right after it is done.

    Any help or insight is greatly appreciated.

    P.S. We have no other problems with any of the other waste lines in the house.

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    The drum trap is not vented correctly.
    You can't drop the pipe downward before the vent. The vent needs to be within five feet, and the grade needs to be 2% or 1/4" per foot. Using fittings the way you have has created an illegal S trap. You should add an AAV there.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    You created an "S" trap which siphons the water out of the trap every time the washer drains water. And, theoreticlly, it could be siphoned when whatever is to the right of the washer drains also. If it is sucked dry you will get sewer gas into the room. You also do NOT need a drum trap and a "P" trap would be immensely better.
    Last edited by hj; 04-17-2012 at 06:39 AM.
    Licensed residential and commercial plumber

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    In the Trades dave36's Avatar
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    Many people assume that this smell is a result of problems with the sewer. However, the smell might be coming from built up bacteria that sits around the sealing. Grocery stores sell specific types of detergent that will clean out the bacteria.

  5. #5
    DIY Junior Member resolaru's Avatar
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    Thank you, Terry & HJ. I don't quite understand. The vent (main stack) is only 2 feet away, so I thought this was ok (main stack is visible on the far left). Do I not need a drum trap and should replace with a standard trap? The line coming from the right comes from a laundry sink, which has a studor valve for a vent. What is an "AAV"? If I had to, I could redo the PVC on the main vent on the left and tie into it just above this line, so it's on it's own run.

    Thanks for your advice.

  6. #6
    DIY Senior Member Smooky's Avatar
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    If the pipe that comes out of the drum trap did not slope down at a 45 degree angle but just went straight over to the vent pipe it would vent properly. Where the pipe exits the drum you need to tie in a vent. The way it is now the drum works like a mini toilet, when water starts to flow through it siphons the trap dry. If there was a vent the trap would stay full of water and the sewer gas would not enter the living space. A studor vent is an Air Admittance valve (AAV)


    http://www.nachi.org/gallery/plumbin...pipe%20(1).jpg
    Last edited by Smooky; 04-19-2012 at 11:51 AM. Reason: added link

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    My inlaws had a washing machine that would stink when it was used and somtimes when it was not used. Nothing to do with the plumbing......it was the machine. She replaced the machine with another standard clothes washing machine and the stink went out the door with the old one. She tried everything to kill the smell but no dice......it was an older machine so she replaced it.

    The O.P. does have a plumbing issue but that may not be the only issue.

  8. #8
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by Hackney plumbing View Post
    My inlaws had a washing machine that would stink when it was used and somtimes when it was not used. Nothing to do with the plumbing......it was the machine. She replaced the machine with another standard clothes washing machine and the stink went out the door with the old one. She tried everything to kill the smell but no dice......it was an older machine so she replaced it.

    The O.P. does have a plumbing issue but that may not be the only issue.
    I agree. The new front loaders need to have their door gaskets wiped dry after each use, and the door left open for it all to dry out. The way the gaskets are molded, the water sits in them unless wiped, and you'd never think it, but they can get real smelly. My wife's LG washer sumthin/sumthin model 3100, is 3 years old and never smelled, yet many other purchasers of this same machine have given it bad reviews based on the smell. You also need to drain the water that is in the lint strainer gizmo in the front at the bottom every so often. My wife also uses those tablets that clean the drum. The washer itself even has a special program cycle for "Tub Clean"
    Plus, the newer machines need to have the HE detergent used (marketing crap?) because regular detergent creates too much suds and using less regular to avoid the sudsing gives less cleaning. It seems that they may not be lying about having to use the HE detergent. We've had a couple of old front loaders many years ago; they never had any smell.

    OR, maybe this thread is a plumbing problem, or maybe both as Hackney says.
    I am definitely not a pro plumber, but I am a pro crastinator

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    Could be a #3. Dead rodent up inside the machine.

  10. #10
    DIY Senior Member chefwong's Avatar
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    A question and a POV.

    A laundry standpipe is new to me...always had it in sinks.
    Does the hose go into it and does the *space* around the discharge with hose need to be sealed (assuming P trap) is doing the work.
    Or does one use the supplied curved U piece to hang the discharge pipe into the line.

    For the OP - if using frontload. Peel back the rubber gasket and try to see how clean or DIRTY the outer drum is.
    If you see muck, and it won't take alot of looking if you have buildup....then it's the washer. The key to FL is to keep the door open, wipe the gasket, use Hot Water, correct soaps, etc. If your soap dispenser comes outward, I pull mine out halfway at times to let the air circulate.

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    FWIW, my front loader does not smell. I leave the door open for awhile after the last load, and it has a silver ion rinse option - silver ions kill bacteria, viruses, and mold, so that helps. Don't use it on every wash cycle, but often enough where, so far at least, I've not had a problem.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member resolaru's Avatar
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    Quote Originally Posted by Smooky View Post
    If the pipe that comes out of the drum trap did not slope down at a 45 degree angle but just went straight over to the vent pipe it would vent properly. Where the pipe exits the drum you need to tie in a vent. The way it is now the drum works like a mini toilet, when water starts to flow through it siphons the trap dry. If there was a vent the trap would stay full of water and the sewer gas would not enter the living space. A studor vent is an Air Admittance valve (AAV)


    http://www.nachi.org/gallery/plumbin...pipe%20(1).jpg
    Thanks everyone. Smooky, now I understand. I didn't even think of that, but I'm sure that could be the problem. Makes total sense now, since the pipe is "dropping" back down into the other pipe.

    As far as my front loader goes, we always leave the door open and wipe the gasket. I don't think the problem is the washer itself, but thanks for the info from the others who mentioned this.

  13. #13
    DIY Junior Member resolaru's Avatar
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    Btw, what is the consensus -is it better to use a drum trap or P trap here? I was told in the past to use a drum trap for cases where water flow is strong (like washer and maybe a shower). Is this not the case?

  14. #14
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by resolaru View Post
    Btw, what is the consensus -is it better to use a drum trap or P trap here? I was told in the past to use a drum trap for cases where water flow is strong (like washer and maybe a shower). Is this not the case?
    In my town drum traps are not approved by code at all. Maybe I'm wrong about that and I mean bottle traps? Don't remember for sure
    I am definitely not a pro plumber, but I am a pro crastinator

  15. #15
    Nuclear Engineer nukeman's Avatar
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    Drum traps are not allowed here either. See Chapter 10 (1002.3):

    https://www2.iccsafe.org/states/Virg..._Frameset.html

    A p-trap with a proper vent is what you want here.

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