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Thread: Sewer Gas in Shower

  1. #1

    Default Sewer Gas in Shower

    Help - anyone!
    I have lived in this house 4 months. It is only 2 years old.

    I have a strong sewer odor in my master shower - only when it is in use and draining. The odor is so strong that it stinks up the connecting bedroom. There is water in the trap when not in use. I have 2 other bathrooms that are used frequently with no odor. The house and shower is on a concrete slab. We are on city services.

    I have had a plumber out 5 times. We have tried various things. The first time, we scrubbed and sanitized the drain. (bleach,vinegar, draino ,etc) The second time, we ran a smoke test down the vent pipe. No leakage around toilet, sinks or shower. However, we had smoke at the air flow tub. It is a tub with an auto vent. ( the wall is a half wall and no way to vent up and out of roof) It appeared that someone had removed the inside of the auto vent. Just the plastic top casing was glued to the top of the vent pipe? Were the previous owners chasing the same problem? I know that venting and suctions are related, so I wonder if they took it off to avoid some sort of siphoning?

    When the shower is in use you can hear the water draining and it sounds unusually loud to me. Could it be that the p trap is not long enough, or too long?

    Replacing the auto vent did nothing for the shower.

    Next, we raised the vent pipe on the roof in case there was a back draft to the venting. No good - worse than ever.

    Then we ran a camera through the sewer line, appeared to be fine with no blockage. We ran the camera through the vent pipe with no visible problems.

    We had a shower tile repair man out to see if it was the shower pan. No luck. He said it appeared to be fine. The smell was not consistent with a pan problem. It is definately sewer gas.

    One other thing that concerns me is the fact that all of the plumbing has been rerouted through the ceiling, which could indicate a previous slab leak. Would there be residual problems from that?

    You can sense my desperation. Any help would be appreciated.

  2. #2
    Homeowner geniescience's Avatar
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    Quote Originally Posted by Kim
    ... However, we had smoke at the air flow tub. It is a tub with an auto vent. ( the wall is a half wall and no way to vent up and out of roof) It appeared that someone had removed the inside of the auto vent. Just the plastic top casing was glued to the top of the vent pipe? Were the previous owners chasing the same problem? I know that venting and suctions are related, so I wonder if they took it off to avoid some sort of siphoning?

    When the shower is in use you can hear the water draining and it sounds unusually loud to me. Could it be that the p trap is not long enough, or too long?

    Replacing the auto vent did nothing for the shower....
    Well, you have certanily worked hard at describing symptoms and diagnosing. Kim

    Was your plumber a Master Plumber?

    To me, this is an interesting challenge, to work with you to figure it out. The part I quoted above is the where I would spend my time, if I were to come over and start poking around.

    Who was the plumber thast the previous owners used? What does the original builder say? Were other houses build by him at the same time? Sooner or later you will get another idea, or one of your previous fixes will be re-done differently... i hope.

    My unprofessional opinion.

    David

  3. #3
    In the Trades Bob NH's Avatar
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    If it is a tub with shower, it is possible that you have something growing in the overflow. I have had that problem with lavatory sinks.

    If you have a tub with overflow, take the overflow cover off and get a semiflexible brush that you can run down the overflow with bleach on it to scrub it out good. If no brush available, put a small rag VERY SECURELY (you don't want to lose it and make a plug) on a coat hanger and use that.

  4. #4

    Default Don't know previous plumber.

    David-

    Unfortunately, the previous owners are not returning my calls. I have not contacted the builder, yet. We have had various other problems that they were not helpful with.

    I have a call into the building permit dept. for our city. I am hoping they can give me info - who did the orig. plumbing, if it passed inspection, etc.

    I got a second opinion an hour ago. They said they did not know what was causing the problem, but there is a drain flap that can be installed. Basically, it is a rubber flap that stays closed in the drain unless water is draining. The pressure of the water on the flap opens it so water can drain, but then closes to prevent gas from coming up. Have you heard of these? Does that just mask the problem?

    KIM

  5. #5

    Default Not a tub/shower combo.

    Bob-

    The shower is free standing. I have cleaned every inch of the shower and drain that is there! The smell does not occur when the shower is not in use. I really feel that it is a water-draining vs. gas isssue. Have you heard of the part I described to David?

    KIM

  6. #6
    DIY Senior Member chris8796's Avatar
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    Are you sure the gas is coming from the shower drain itself? Could the shower drain be pulling the water out of the trap on the sink?

    It seems a little odd that it only happens when your running the shower.

  7. #7

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    Chris-

    It is VERY odd. The smell is definately the shower. There is no smell at either of the sinks. The shower door is glass and holds the smell in the shower. It escapes only at the top of the door where there is a 4" opening. Otherwise, the shower is completely enclosed. Given enough time, the odor makes it's way into the rest of the bath and bedroom.

    It is almost like you have to be in the shower to get the odor. It takes 10 or so minutes. But, once it starts it grows stronger the longer the water runs?

    KIM

  8. #8
    DIY Senior Member chris8796's Avatar
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    It sounds like there is a second p-trap or at least a dip in the shower drain after the shower p-trap. When you drain water, it pressurizes the gas in the drain and burps it back up the shower trap. If you had a regular vent you probably wouldn't notice, but since you have an AAV, there is no other place for the gas to go.
    Last edited by chris8796; 06-16-2006 at 01:14 PM.

  9. #9

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    Chris-

    What is the solution? Do I have to tear out the shower to find it?

    No chance of matching the tile - discontinued. I would have to retile the whole thing. Have you heard of that drain flap that I described above?

  10. #10
    DIY Senior Member chris8796's Avatar
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    I would check with you local plumber to confirm that is the problem. This is the only thing I can think of that would cause pressurized gas in the drain line, while still allowing the water to pass (and occur only when the drain was draining).

    If it is, the two solutions are:

    1. Dig up the drain and remove any dips or p-traps.

    2. A second poor solution would be to run a regular vent through the ceiling. This would only prevent the symptoms and leave the real problem there. This second trap or dip would eventually cause clogging problems and require you to fix it in the future.

    You might try a quick test, use a flashlight look into the shower trap (hopefully you can see the water) and slowly poorly water into the drain (about the rate the shower delivers) so you can see if large air/gas bubbles are coming up from the trap.

  11. #11
    Homeowner geniescience's Avatar
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    Quote Originally Posted by chris8796
    You might try a quick test, use a flashlight look into the shower trap (hopefully you can see the water) and slowly poorly water into the drain (about the rate the shower delivers) so you can see if large air/gas bubbles are coming up from the trap.
    Interesing what Chris is suggesting, since it will verify 100% that your smell is coming up the shower drain. We all may think it is, but this is further confirmation.

    Please post a line drawing. Do you know where venting is in your drain system? Do you know the slope of your drain line?

    If you do get bubbles and air coming back, will this be more when the flow is high or low?

    Before I offer a whole new batch of hypotheses, can you provide this information?

    David

  12. #12

    Default sewer gas

    I think you should go back to the auto vent and remove the auto vent or AAV and plug the fitting where AAV is.Run the shower and see how that effects the situation,another issue with using an AAV,some of the other fixtures that you speak of are robbing water from the trap of the shower,one more thing that has occurred with AAV's is that microscopic bugs do not allow the disc in the AAV to seat properly therefore sewer gas is emitted into the living area.If there is no break in the pipe and the smoke test only appeared where the AAV is located I think that is the culprit.

  13. #13
    In the Trades Bob NH's Avatar
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    You can check the action of Air Admittance Valve by putting a clear baggie over it and fastening with a rubber band. If the bag sucks in against the AAV when you run water or flush the toilet, then it is trying to work. If the odor doesn't come out with the baggie, then that is the source of the gas.

  14. #14

    Default

    OK. Let me see if I have this right.

    The auto vent that is on the vent pipe, in the wall, for the air flow tub could be the problem. You know that the auto vent is not on the shower vent pipe, right? It does have its own vent that goes out the roof. It also is not on the same wall.

    If so, then I need to go back into the wall and either put a baggie securely over it or cap it off. Then I run the shower the way I normally would to get the smell. If I do not get one, then the problem is fixed?

    Also, I am not smelling the gas in the tub. So we are talking about the same thing?

  15. #15
    In the Trades Bob NH's Avatar
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    I'm not saying that a baggie fixes it. It is an experiment to see if that is where the smell is coming from, and if the vent is working. It actually defeats the Air Admittance Valve.

    Here is my logic.

    Start with the concept that there should be NO air passage from the sewer or drains to your bathroom. The toilet is trapped and all of the drains are trapped and the traps contain water.

    Now the nearest thing to a connection to the sewer is an Air Admittance Valve. If you close that off, then there is NO POSSIBLE air passage to the sewer.

    If you still get the odor, then what source is left? Somewhere inside the bathroom? Bacteria growing in an overflow or on the bathroom side of a trap? A leak in a hidden drain pipe? An open vent hiding in a wall? A failed wax ring on the toilet?

    Is it possible that someone has terminated a vent in the attic and it is coming in via an exhaust fan that is terminated in the attic?

    So, first verify that there is not any airway to the sewer. If you still get the odor, then it must be in the bathroom. Then rule out all of the "in bathroom" possibilities.

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