Sewer Gas in Shower

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Kim, Jun 16, 2006.

  1. Kim

    Kim New Member

    Messages:
    28
    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. 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. Bob NH

    Bob NH In the Trades

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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. Kim

    Kim New Member

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    28
    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. Kim

    Kim New Member

    Messages:
    28
    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. chris8796

    chris8796 New Member

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    Location:
    Illinois
    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. Kim

    Kim New Member

    Messages:
    28
    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. chris8796

    chris8796 New Member

    Messages:
    100
    Location:
    Illinois
    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: Jun 16, 2006
  9. Kim

    Kim New Member

    Messages:
    28
    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. chris8796

    chris8796 New Member

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    Location:
    Illinois
    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. 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. tbplumbloco

    tbplumbloco New Member

    Messages:
    60
    Location:
    Ohio
    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. Bob NH

    Bob NH In the Trades

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    Location:
    New Hampshire
    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. Kim

    Kim New Member

    Messages:
    28
    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. Bob NH

    Bob NH In the Trades

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    Location:
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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.
  16. Kim

    Kim New Member

    Messages:
    28
    BOB_

    Oh, I knew what you meant by the baggie not being a permanent fix. I just forgot to type that - sorry.

    Thanks for the more detailed explanation.

    Let's say that I do the baggie experiment & we don't get the smell. Then, I assume the best bet is to have the auto vent in the wall to the tub capped off. Does the tub not need a vent at this point?

    Something interesting - I have avoided bathing in that bathroom (shower and tub) because it is nauseating. Last night, my little boy wanted to be in the big bathtub, so we gave it a shot. After the tub drained, we had the smell coming from the shower ( we did not do the baggie because I had not gotten your post yet). Also, there was a big bubble that came from the tub drain and what appeared to be a whitish, gritty/powdery substance left in the tub. Perhaps grout that washed down the drain when they were tiling the top of tub?

    Does this confirm your suspicion that the tub vent may be the problem?
    I will go back into the wall today and test it.

    Also, have you heard of the rubber flap thing I have mentioned - to prevent gas in drains?
    Last edited: Jun 17, 2006
  17. Bob NH

    Bob NH In the Trades

    Messages:
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    Location:
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    "Also, there was a big bubble that came from the tub drain and what appeared to be a whitish, gritty/powdery substance left in the tub. Perhaps grout that washed down the drain when they were tiling the top of tub?

    Does this confirm your suspicion that the tub vent may be the problem?"

    The fact that a bubble came from the tub drain tells you that the trap had been siphoned out when you drained the tub, or that there may be a restriction in the drain line preventing the tub from draining properly. There should not be any pressure that will allow a bubble to blow back past the trap or through the water.

    An air admittance valve lets air INTO the pipe when there is a slight vacuum so that the water won't be siphoned out of the trap. http://www.toolbase.org/techinv/techDetails.aspx?technologyID=140
    If something is comimg up through the trap, it could be due to atmospheric pressure equalizing after the water was siphoned from the trap. It could also be that there is a clog in the drain farther downstream that is causing water to be forced back toward the tub.

    In all of this we have been ASSUMING THAT THERE IS A TRAP. It is not inconceivable that someone installed a tub without a trap. Sometimes it is difficult to work under a tub. Sometimes there is little space. Maybe they forgot.
  18. Kim

    Kim New Member

    Messages:
    28
    There is no visible p trap under the tub. I am trying to figure out how to e-mail you a picture of the tub drain. Could the trap be under the slab like the shower? If you can visualize this - The drain pipe comes from under the tub (horizontally) where the drain is. It then ties into the tub overflow (a vertical pipe) to make a t. Then, it continues vertically down into the concrete. The vent pipe is parallel to the drain pipe but in the wall behind the drain and hard to see. It appears that the vent pipe does not connect higher than where the drain goes into the concrete. Is the vent pipe supposed to connect higher than the drain pipe?

    I tried the experiment with the bag. The bag did not cling to the auto vent like I expected when the shower was turned on. Even through an entire shower the bag did not change. The shower again smells like gas.
  19. stick line diagram, please.

    kim,
    i hope to help diagnose this. Can you draw a simple stick diagram? I use Paint. There is a lot of text to read through, from the beginning. Someday soon I will get around to it. A drawing wil re-cap everything quickly. Should help everyone else too.

    Idea: since you just took a shower, and the smell came back, can you try this the next time: put a plastic bag and a towel over the drain, let an inch or more of water build up, and then "control" closely how much water you let go down the drain, while watching for bubbles coming back up. Some water will trickle through before you start releasing it, so watch for bubbles the whole time.

    Several possible outcomes: Smell, no or yes. Bubbles, no or yes. At least four outcomes; more are possible (e.g. bubbling from tub). Later, to do an even more complex experiment, you fill the tub and you let it drain slowly while you repeat the same with the shower.

    Meanwhile, hope you can draw a few sticklines to show us all in summary recap what you have, as far as you know. Leave the p-traps out if you aren't sure they are there.

    David
    (Edit: I mean a line drawing to show pipes only. Drain and vent pipes)
    Last edited: Jun 17, 2006
  20. Kim

    Kim New Member

    Messages:
    28
    I have tried to draw the picture on paint and I have digital pictures. I am a computer novice so I do not know how to transfer them to this. Can you help?
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