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Thread: Couple Plumbing Questions...

  1. #1

    Default Couple Plumbing Questions...

    My GFs family wanted me to do some plumbing for a sump pump system and also run a drain for a washer. Both are in the basement. No big deal there.

    There is one main 3" drain stack in the basement which disappears into the ground. There is 1 2" trunk that is only about 8" then reduces to 1.5" piping so the majority of this trunk is 1.5". There are 3 1.5" brances coming off this one trunk that is also 1.5". I find this very bad and im about to replace the truck and make it a full 2" with 1.5" branches. Their sump pump was originally plumbed into this truck so thats where I left it. I find that when the pump kicks on, it seems to create a vacuum and sucks the water out of the sink trap and you then hear a bunch of gurgling noises.

    Now, my question is this. According to the math it seems I should only have 2 1.5" pipes on a 2" pipe correct? So I was thinking of making TWO 2 inch trunks of the main stack and have 2 1.5" branches off each trunk. Should I do it this way or should I have all 4 go into the 2"?

    The 1.5" drains are, bathroom shower and sink(one pipe), kitchen sink, sump pump and washer drain.

    Typing this out I think I just answered my own question.

    My next question is this. I don't know who did the plumbing before but its really messed up. There is also no vent in the plumbing system anywhere. How important is a vent?

  2. #2
    Homeowner geniescience's Avatar
    Join Date
    Nov 2005
    humid summers hot, humid winters cold


    Quote Originally Posted by jgray152
    ... also no vent in the plumbing system anywhere. How important is a vent?
    sounds worse than you can imagine. Learn more about vents quick! Show them what you learn; if the homeowners don't understand it they may think you're just being perfectionist. Fix venting before adding more drain fixture units (DFU's).


  3. #3
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default drains

    IF there are really no vents then that is why the pump's discharge is creating a Bournelli effect and sucking the water out of the traps.

  4. #4


    I was actually thinking back to the layout of the plumbing and I think there is a vent. If I remember I think its a cast iron pipe. I Will have to double check.

    Also, is there a good placement for vents? Such as between two 1.5" branches going into a 2" trunk? Basically should I add 2 vents and combine the 2 extra vents to the main vent?

    The vent I think is off the top of the 3" main. I will have to double check.

  5. #5


    Quote Originally Posted by jgray152
    There is also no vent in the plumbing system anywhere. How important is a vent?
    Kudos for trying to help yr gf's family. No disrespect, but if you're asking this question, reconsider if you're the right person for this job. At the very least, you gotta learn ALL you can about this, and check w yr construc office whether an unlicensed person can do this plumbing work.

    If their house was inspected at construction, and if they've been using the plumbing for a long time without much siphoning (besides the sump) or odor problems, I seriously doubt there's NO vent whatsoever. Are you sure yr just not seeing it? The vent's might all take off in the walls, in which case you wouldn't see them except for in the attic (if there's one) or as they penetrate the roof.

    I'm a diyer myself, so I hope I'm not coming off bad. I don't mean to.

    (important note: I'm not a pro)

  6. #6


    I know the intension of the vent, I was just hoping there was a really small chance you didn't need it if the pipes were big enough but even then I can see issues. I just didn't want to have to put one in. I would have left that for a real plumber since im not about to put a whole in a roof

    There IS a vent though. Its a cast iron pipe on the top of the main stack. So no issue there. I just had to remember


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