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  1. #1
    Jeff Eastman's Avatar
    Jeff Eastman Guest

    Default vent on wrong side of p-trap

    Last edited by Jeff Eastman; 12-20-2007 at 07:17 AM.
    Elite MGA Home Inspector E&O Insurance

  2. #2
    Join Date
    Mar 2007
    Location
    Dallas, Texas
    Posts
    4,112

    Default Re: vent on wrong side of p-trap

    Trap can be sucked dry allowing sewer gas to get past the water seal in the trap.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  3. #3
    Join Date
    Mar 2007
    Location
    Dallas, Texas
    Posts
    4,112

    Default Re: vent on wrong side of p-trap

    If the drain is on the negative pressure side of AHU, then you can draw sewer gas and/or attic air into the system.
    If the drain is on the positive pressure side of OAHU, then you lose conditioned air into the attic while it is running and air can move either way during off cycle.
    The trap comes first, then the vent downstream of the trap just like in a sink or other fixture. Keep the conditioned air in the air conditioner.
    Of course there should not be sewer gas since the condensate drain should discharge into a trapped drain with an air gap.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  4. #4
    Richard Rushing's Avatar
    Richard Rushing Guest

    Default Re: vent on wrong side of p-trap

    Jeff,

    Usually in new construction you will have the builder tell you that they install that vent for the homeowner to add bleach every Quarter to 6 months.

    Tell them that that's ok, but they will need to cap it off and tell the homeowner to remove the cap when they add the bleach, then replace it when they are done.

    Now, the issue still remains that they need an adequate vent AFTER the trap to allow for proper drainage.

    The only thing that is accomplished if the vent is BEFORE the trap is that air escapes into the attic and as Jim stated, the vent can dry out. When the system is under negative pressure meaning is draws air thru the line, the primary condensate drain line siphons air thru the line, possibly bringing some pretty nasty smells from the sewage drainage into the unit and re-distributed into the home... Nasty stuff.

    Richard


  5. #5
    Richard Rushing's Avatar
    Richard Rushing Guest

    Default Re: vent on wrong side of p-trap

    Sorry Jim, I was typing as you were posting...

    RR


  6. #6
    James Duffin's Avatar
    James Duffin Guest

    Default Re: vent on wrong side of p-trap

    In most cities you can not dump condensate into the sewer system because it is clean water....do you guys see this setup very often?


  7. #7
    Join Date
    Oct 2003
    Location
    Rockwall Texas
    Posts
    4,517

    Default Re: vent on wrong side of p-trap

    Clean water not allowed in sewer systems?


  8. #8
    Join Date
    Mar 2007
    Location
    Philadelphia PA
    Posts
    3,177

    Default Re: vent on wrong side of p-trap

    A lot of municipalities around here don't allow sump pumps to discharge into the sewer, and probably AC condensate as well. The idea being - if everyone does it, the water treatment plants get overloaded with water that don't need no stinkin' treatment!

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

  9. #9
    Join Date
    Mar 2007
    Location
    Connecticut
    Posts
    1,822

    Default Re: vent on wrong side of p-trap

    correct, no condensate, sump, or water treatment discharge allowed. City systems can't handle the overload.
    Septic systems can't handle the mineral build up.
    Now back to the real world.


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