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

  1. #1

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

    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. #2
    Plumbing Designer FloridaOrange's Avatar
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    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.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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    Moderator & Master Plumber hj's Avatar
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    Default 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.

    Last edited by Terry; 05-31-2012 at 04:11 PM.

  4. #4

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    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.

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    Plumber patrick88's Avatar
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    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?

    I would do that.
    I'm just starting to work with an old friend of mine to bring solar electric and hot water systems, wind turbines, Flex Fuel Boilers, batteries, hydroponic gardening, books, pellet grills and more. Also the parts for DIY installation.

  6. #6

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    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. #7

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    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...
    Last edited by achtungpv; 02-13-2008 at 08:41 AM.

  8. #8

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    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?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Retired Defense Industry Engineer jadnashua's Avatar
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    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
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    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?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12

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    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. #13
    Forum Admin, Expert Plumber Terry's Avatar
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    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. #14

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    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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