whole house trap

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ddurand, Feb 23, 2007.

  1. ddurand

    ddurand New Member

    Feb 23, 2007
    The house I am looking at buying has a whole house trap in the 4" drain pipe after all the fixtures in the house but before the kitchen sink and dishwasher. I have never seen a whole house trap in a house before. The washing machine drain pipe has no trap and smells from time to time. I was told its from residual stuff on the 10' of drain pipe before the whole house trap and not gas from septic tank. Also right next to the whole house trap is a elbow and then an open 4" vertical pipe (between fixtures and whole house trap). I was told this is another vent and should just be vented through the stil in the basement or a pop up vent installed. Since its after all the fixtures it will not help with a the vacuum created when a toilet is flushed, so what is it there for?

    If I install a trap in the washing machine drain line I am not sure how to vent it. Its the last fixture in the 4" drain pipe (farthest from septic).

    Lastly, someone put a tee and in the attic connected the bathroom fan to the 4" vent stack via white flex hose. It may work, but just seems odd.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Can't help with all of the problems, but connecting the bathroom vent fan to the sewer vent line is NOT correct - it must be run separately.
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    It should be on the outlet side of the whole house trap, and without it the septic tank will become a closed system and nothing will drain. We remove whole house traps whenever we find them.
  5. ddurand

    ddurand New Member

    Feb 23, 2007
    whole house drain

    The open pipe is on the house side of the whole house trap rather than the septic side. However the whole house trap is really an almost whole house trap, as its after all fixtures but kitchen sink. So I assume the septic can vent through the vent used by the kitchen sink.
  6. Gary Swart

    Gary Swart In the Trades

    Sep 1, 2004
    Yakima WA
    I'm not an expert on this, but from following this forum for as long as I have, one of the bits of knowledge I have gathered is that a whole house trap is way out of modern use. I would advise you look into removing it and installing standard p-traps in your house. Another bit of knowledge, bathroom and kitchen vents must go outside separately and not be connected to a sewer vent.
  7. ddurand

    ddurand New Member

    Feb 23, 2007
    venting a whole house trap

    If one did have a whole house trap, it would seem one would need a vent on the septic side, in addition to all fixture drains being vented.

    And in my case, the whole house drain does not eliminate the bad smell, which I assume is various crud coating the 10' of pipe in the house before the whole house trap.
  8. TedL

    TedL New Member

    Sep 17, 2006
    NY Capital District
    Is the "whole house trap" in question the same thing as the running trap, which is in additional to individual traps?

    Or is it some ancient configuration that came before individual fixture traps?

    My current and recent homes both have a running trap, which our code apparently required at least through 1984, when the newer one was constructed.
  9. ddurand

    ddurand New Member

    Feb 23, 2007
    This is pretty new construction, less than 5 years old. Never heard it called a running trap. Its in addition to the normal traps for each fixture. Except for the one for the washing machine drain, that maybe they forgot.
  10. enosez

    enosez Member

    Jan 27, 2007
    Supv Maint Oper
    Long Island NY
    Am I in trouble.

    Both our houses have septic systems and "house traps" made from 3" and 4" PVC fittings respectively. There is a "fresh air vent" just before the house trap on the 3" line in one house. In the other, I have 4" PVC house trap with no fresh air vent other than a piece of 2" which transitions to galvanized and runs along the outside of the outside of the house as a vent. (House is dated 1901).

    Both systems have been running fine for the last 5 years since weve owned both houses.

    Should I be worried??
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