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  1. #1

    Strong sewer smell in office building

    We have been in our building for 11 years. We have random strong sewer gas smells in the office which seem to happen on a no wind day. The roof has a flat top and our HVAC guys have been up there numerous times trying to figure out what is wrong.
    They have raised the vent stacks and installed charcoal filters on them. They have opened up a few walls to modify the vent pipes but the stink continues.
    Our building is at the bottom of a valley and we’ve been told that it looks like the city sewage gas is coming out of our vent stacks creating more than a usual amount of sewage vapor.
    No one seems to know what to do.
    When I go up there (I’m no HVAC professional) I see the following. A flat roof with walls about a foot tall. If the gas is heavy which I believe is true then I see the gas pooling on the roof of the building. We have several Lennox GCS16’s with what I believe is a horizontal Economizer Damper on the side. (I just downloaded the manual and that is what I figured the filter on the side was – I may be wrong). If this is an economizer then from what I read it will be sucking in fresh air from the outside or in our case from a pool of stink.
    Does my theory make any sense? Your opinions would be most appreciated.

    Thanks,
    Name:  el stinko.jpg
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  2. #2
    Join Date
    Feb 2006
    Location
    Atlanta,GA.
    Posts
    926
    yes that would be the intake vent, sewer gas /methane is light and will rise, I dont see any raised sewer vent pipes and that looks like one close to that intake

  3. #3
    The vents were raised to about a foot and run down the middle of the roof. Name:  vents.jpg
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Size:  30.5 KBName:  vent close.jpg
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  4. #4
    Join Date
    Mar 2011
    Location
    Virginia
    Posts
    93
    The vents need to be at least 10 ft from the intakes, you can raise them up which looks easiest.
    You also need to check any drains to make sure they are not dry.
    Typical floor drains, parking lot drains etc.
    Use mineral oil in them if they are seldom used.
    That will last longer than water and provide a better seal.

  5. #5
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    880
    Not to put any HVAC people out of work, but a would also get a Master Plumber to 1) look through the original as builts, co-ordinate those prints with any build outs. 2) If there is any location were the sewer smell is dominate check all the drain lines, tie ins above the ceiling grid along with vent piping. 3) Has any of the HVAC contractor's check building static pressure ? If it is positive, does it stay positive ? If it is negative it will suck the fume out of the vents or through dry traps. A very good point about using mineral oil in any drains that are dry and not used. There is a lot more to plumbing then the three basic rules
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  6. #6
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,145
    First thing I thought of was dry floor drains. I'd like to add don't forget floor drains in the bathrooms. I would have thought they would be separate from the sewer pipes, but we were in one building and traced the smell to that. Ga1279, I'm not a plumber. What are the three basic rules?

  7. #7
    Join Date
    Mar 2011
    Location
    Virginia
    Posts
    93
    I am a Master plumber and a Master HVAC guy and most plumbers I know would not have a clue as to where to start, no offense intended.
    I just know I have solved many building issues by looking at all of the issues because I have studied them all.
    If he makes it like code requires and goes from their and checks all of his floor drains for being dry he has made a huge step forward!
    There is telling what you will find.
    I make bets on jobs like these because I always figure them out.
    I have not fond one I could not fix!

  8. #8
    Join Date
    May 2009
    Location
    In the Hudson Valley of New York
    Posts
    2,048
    We have our own fiasco at a national chain restaurant. The are using Trane units with the Economizer intake about a foot or 2 from the roof. The plumbers raised the stacks 6' high, and when you get down near the roof the odor is worse, sewer gas is heavier then air, so you really need to get it off the roof, or away from them units.

    http://aetinc.biz/newsletters/december-2009/

  9. #9
    Join Date
    Jan 2005
    Location
    Emerald Coast
    Posts
    965
    Quote Originally Posted by perryaire View Post
    ... checks all of his floor drains for being dry he has made a huge step forward!
    There is telling what you will find....
    .

    Hmmm, calm days. Dry traps would be prime suspects.

    Check the OA filters. The filter on the economizer with the arrow in your picture
    looks pretty plugged up compared to others.

    Do you have any equipment in the building that exhausts building air other
    than fart fans? Is this a medical facility?
    ..
    Do not attempt vast projects with
    half vast experience and ideas.
    ...

  10. #10
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
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    4,544
    Quote Originally Posted by bikenbc View Post
    The vents were raised to about a foot and run down the middle of the roof. Name:  vents.jpg
Views: 1863
Size:  30.5 KBName:  vent close.jpg
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    That back vent in the pic looks close to that intake. I would temporarily raise the vents to 24" above your existing unit tops and see what happens after a few days or weeks. If the odor continues then oil the traps as stated by others. If the odors persist you might have an open cleanout behind a wall or open venting above a ceiling somewhere. Peppermint oil can help find the open pipe. Does your waste require storage and pumping?
    Some Talk, Some Do
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  11. #11
    Join Date
    May 2009
    Location
    In the Hudson Valley of New York
    Posts
    2,048
    Quote Originally Posted by bikenbc View Post
    We have been in our building for 11 years. We have random strong sewer gas smells in the office which seem to happen on a no wind day. The roof has a flat top and our HVAC guys have been up there numerous times trying to figure out what is wrong.
    Fact remains, sewer gas is heavier then air.

  12. #12
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,114
    I see your units have P traps but they don't go to anything. They are also not built right. The end of the P trap should be lower then the start of the P Trap. I do not know if the RTU fans are sucking air in through the P trap but it could compound your issue.

    P traps


    Name:  condPtrapVent.jpg
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    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  13. #13
    Join Date
    Mar 2013
    Location
    Springville, NY
    Posts
    3,829
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here.

    You can find the rules for posting and qualifications here.

    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 04-07-2013 at 08:50 PM. Reason: Non Pro * Member

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