Problem with sewer gas from dishwasher

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by cricket, Sep 9, 2008.

  1. cricket

    cricket New Member

    Sep 9, 2008
    We moved into an older house three months ago. We noticed a nasty smell from the dishwasher. It would come and go. The previous tenants had many cats so we thought it was lingering smell from that or even a dead mouse or something. For awhile the smell went away but the other day it was back and very strong. We realized then that it was sewer gas. We used a lot of water last night and last night the smell was the strongest we've ever had. The strongest smell is from the dishwasher. It's a small house and the bathroom is on the backside of the kitchen. The dishwasher and the shower share a wall. Sometimes the smell is in the bathroom too. We planned on remodeling the kitchen at some point but we can't take the smell--and it can't be healthy--so we need to do something now.

    We checked the vent pipe on the roof. It wasn't clogged although there was water at the bottom of it. Is that normal? If I pull the dishwasher out, what do I look for? It looks like it is hooked up correctly but I don't see a loop in the drain line to keep backwash from entering the dishwasher. I can't imagine backwash smelling this bad though. The drain hose for the dishwasher is hooked up to the sink drain and it is above the trap. The house was empty for about three months before we moved in. I don't know if that gives anyone any clues. All of the waste water drains under a second bathroom in the house before going outside. I've never noticed a bad smell in that bathroom but we don't use that bathroom.

    I'd like to at least try to pinpoint the problem so we know what we are dealing with. Thanks for any help you can give me!
  2. Master Plumber 101

    Master Plumber 101 In the Trades

    Aug 11, 2008
    If it is sewer gas the dishwasher would be connected to the drain system incorrectly. Look to see how the dishwasher discharges into the drain system. It should go into a dishwasher tail piece after it discharges through an airgap. There might also be another code approved method, but one way or another should discharge to a trap after one of the above.
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  4. krow

    krow Plumber

    Feb 11, 2008
    Ontario, Canada
    Assuming your P-traps are vented correctly and your hose is connected upstream of the trap, your smell is not sewer gases.It could be 1 of 2 things.

    1) you could have a build up of sludge in your kitchen sink drain and when the dishwasher discharges the hot water, it aggitates the sludge making it smell.

    2)Your drain hose could have built up a bit of sludge and everytime hot water passes, it aggitates.

    I beleive there is a product out called "Afresh" to clean out the discharge hose of the front loader washing machines. I have never heard of anyone using it for dishwahers, but it may be worth a try. Check the instructions to make sure it is safe to use in dishwashers.
  5. krow

    krow Plumber

    Feb 11, 2008
    Ontario, Canada
    You could try this. You would probably have these on hand

    Cleaning A Dishwasher
    1 Serving


    1 c bleach
    1 c vinegar


    Cleaning the interior of your automatic dishwasher is a two-step method, so
    please read the entire directions before beginning.

    While cleaning, you can wash any cloudy glassware, ceramic or china dishes
    that could use the same treatment, but don't put in any silver, plastic,
    aluminum or brass. They may discolor and then you'll really have a mess on
    your hands.

    Step 1: Pour one cup of bleach into a bowl and set the bowl on the bottom
    rack of the dishwasher. Run in through the "wash" cycle only. Do not dry.
    If your dishwasher cannot be stopped after a cycle, then punch the "cancel
    drain" button.

    Step 2: Fill the bowl again, this time with one cup of vinegar. Let the
    dishwasher run through the entire cycle this time.

    You will find the discolorations, film and buildup on the interior of your
    dishwasher, as well as on your dishes, even down to the gunk that settles
    in cracks and crevices, gone.

    A word of caution: Don't be in a hurry and combine the bleach and vinegar
    for a one-step process.
    Last edited: Sep 9, 2008
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