in-wall drain vent allowing septic smell to seep in?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by acthungpv, Oct 26, 2007.

  1. acthungpv

    acthungpv New Member

    Messages:
    3
    Had a bathroom remodel done. To make a long story short, since we removed a false ceiling that hid a bend in the old shower's vent to the roof that would have been exposed if it was continued to be used, the plumber put in an in-wall vent on the new shower's drain.

    Would this type of vent allow septic gases to seep in? The wall where it is located backs the master closet and there is a faint smell in there. Should I just go in the attic and reroute the old vent pipe so it lines up with wall and reconnect it to vent outside?
  2. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    If your talking about an air admittance valve (studor vent) it shouldn't let sewer gas out. It's a one-way valve. If you can vent naturally that's the best choice.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,311
    Location:
    Cave Creek, Arizona
    vent

    It is probably not that device, but an "inwall vent" is not supposed to be in the wall, unless you have some access to it so it can be tested and/or replaced when necessary.

    [​IMG]
    Last edited by a moderator: May 31, 2012
  4. acthungpv

    acthungpv New Member

    Messages:
    3
    After looking at pictures on the Web, it is an air admittance valve.

    The only other thing I can think of is that we plugged the old shower drain with concrete (we removed the old shower stall and added this space to the master closet). Could fumes seep through the concrete somehow? It'd have to go through the concrete, thinset, and tile though.

    Both vanities, toilet, and new shower pan are used daily and surely have water in their p-traps.
  5. patrick88

    patrick88 Plumber

    Messages:
    836
    Location:
    Webster Ma.

    I would do that.
  6. acthungpv

    acthungpv New Member

    Messages:
    3
    Last night after showering, the septic smell was very strong. Could the valve not be functioning correctly and allowing water to be suctioned out of the shower's P trap? However, I am not sure as to the source. I checked all sinks, toilet and shower drain and could not smell anything near any fixtures. So, the source stopped leaking fumes I guess.
  7. achtungpv

    achtungpv New Member

    Messages:
    4
    So I removed the air admittance valve and reconnected the pipe to vent out the roof. After re-sheet rocking the closet wall where I'd cut through to access the pipe, I was really obsessive and before I put on the base board, I caulked the bottom of the sheet rock where it meets the tile to assure no air could get through just in case the smell wasn't from a faulty AAV.

    There is STILL an occasional faint smell in the closet! I have no idea at this point where it could be coming from. That is the only vent pipe that backs the closet. It originates in the closet so it is not coming from either vanity, the shower, or the toilet (which I caulked around the bottom just in case).

    Any ideas?

    Here's a pic of the bathroom if it gives anybody any ideas of the source of the smell...
    [​IMG]
    Last edited: Feb 13, 2008
  8. achtungpv

    achtungpv New Member

    Messages:
    4
    Finally had a plumber come out yesterday. He said that the cutout space in the slab that was made for the shower drain and vent pipes should have been backfilled with sand. He thought the smell probably came from this space since the P-trap, vent, etc. had no problems. So, I'll just go buy a bag of sand and fill in the space.

    Does this sound like a legitimate possible smell culprit?
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,830
    Location:
    New England
    Unless the tub or drain line was leaking, or you've got under slab moisture problems, the soil probably wouldn't smell. The pipe may have problems. Sand won't do anything IMHO. That area sometimes gets filled to keep out critters, but sand wouldn't do it.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,830
    Location:
    New England
    Unless the tub or drain line was leaking, or you've got under slab moisture problems, the soil probably wouldn't smell. The pipe may have problems. Sand won't do anything IMHO. That area sometimes gets filled to keep out critters, but sand wouldn't do it. Is
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,830
    Location:
    New England
    Unless the tub or drain line was leaking, or you've got under slab moisture problems, the soil probably wouldn't smell. The pipe may have problems. Sand won't do anything IMHO. That area sometimes gets filled to keep out critters, but sand wouldn't do it. Is the soil perceptably wet?
  12. achtungpv

    achtungpv New Member

    Messages:
    4
    So, 6 months ago, I cut out a 12"x12" piece of sheet rock to access where the drain pipe goes under the slab and filled the space around the pipe with sand. No smell whatsoever after do that. Being lazy, I didn't fix the drywall cut out until a week ago. IMMEDIATELY THE SAME DAY, the smell returned and comes back every couple of days.

    Seriously, what on earth is going on? Do I just need to put a screen vent on the dry wall to allow air flow into the wall?

    This is the most bizarre situation I've ever seen.
  13. Terry

    Terry Administrator Staff Member

    Messages:
    14,813
    Location:
    Bothell, Washington
    An air admittance valve need ventilation.
    If it's in the wall, it needs a grill access to allow air to pull down the vent.
  14. achtungpv

    achtungpv New Member

    Messages:
    4
    I removed the air admittance valve 6 months ago and reconnected the vent to to the roof.

    I think I'll go ahead and put in a vent to get air flow in the wall. I have no idea why that'll work but that seems to be why there was no odor when the there was an opening in the drywall.
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