Sewer Gas Smell After Flushing

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by doughboy63, Aug 26, 2006.

  1. doughboy63

    doughboy63 New Member

    Messages:
    34
    After we flush the toilet in the full hall bath there is a very strong sewer smell in the room. It goes away with time and then when you flush, it is back again. The toilet does not rock. Would the wax ring be the first place to start and replace that? No water leaks at the toilet. Any other trouble shooting or different approaches to start with, or just do the ring and go from there? Thanks.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    After flushing, is the toilet bowl still full? IF you run some water in the sink after the toilet is flushed, does it help? Can you hear anything from the sink when you flush?

    The toilet's trap is in the toilet. The sink's is underneath it. Each should have its own vent connection. If they aren't hooked up right, running water down one can cause the other's to siphon out the trap, giving a path for sewer gasses into the room.

    If the toilet's wax ring was compromised, it could let sewer gasses in all of the time, not just when you flush. It still could be a problem, but is not high on at least my priority list.
  3. doughboy63

    doughboy63 New Member

    Messages:
    34
    Thanks for the reply Jim. I am not sure what you mean by the bowl still being full. It flushes normally, and having a normal water spot in the bottom after filling. I thought about it siphoning the sink. The sink actually drains really slow which I don't know if it is related, but I did fill the sink and then flush the toilet. The smell still came and there was no sudden increase in draining that I would expect if it were siphoning. But what do I know right, that is why I am here. I have not tried this on the tub however. I have smelled all the drains and around the toilet and cannot pinpoint where the smell is coming from.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    The toilet's water spot is what is blocking sewer gas from coming up the pipe. Having a bowl full of water in the sink, though, does not provide the same effect - gasses can still come up through the overflow since it has its own path to the trap. The sink's trap is that loop underneath. If the vents are not installed properly, flushing the toilet can siphon the water in the trap out by the sink, and then provide a direct opening to the sewer through either the normal drain opening or the overflow.

    Since that sink drains slowly (has it always done this?), it sounds like you may have a vent problem that is draining the sink's p-trap.
  5. doughboy63

    doughboy63 New Member

    Messages:
    34
    The sink has always drained slow. We have lived here only a few months and it has been lower on the priority list. This sink actually doesn't have an overflow. It is marble and just has the drain. This house was built in '57 and there is a stack coming out the roof above this bathroom. What steps should I take to diagnose this venting issue and go about fixing it?
    thanks
  6. Go up on the roof and check the vent pipe for leaves, debris, birdnest, etc. and remove anything that you can by hand.
    If there is debris down in the stack that you can't reach, break it up with a heavy-duty plumber's snake, and then flush the stack pipe down with a water hose sprayer.
    Good Luck!
    Mike
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    odor

    Since it is a full bath does the tub or shower get used periodically? If not then the trap has dried out and that is the source of the odor.
  8. doughboy63

    doughboy63 New Member

    Messages:
    34
    Mike, I went up on the roof this morning before posting. I could not see anything in the stack and ran my little DIY snake as far as it would go. It went down pretty easy. I will try the hose after dinner. HJ it is used everyday as a shower. Thanks guys, I will post after I try the hose.
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