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Thread: Venting a horizontal line with height restriction

  1. #1
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default Venting a horizontal line with height restriction

    In another thread, Terry once said:

    "Fittings on their side (horizontal) and below grade should be wye fittings.

    When rolling a vent off with a wye, most of the time, you would use a 45 and make sure that the rolled vent is above the flow line of the waste line.
    For the toilet, that would be wye with 45 pointing the same direction as the pipe, and running toward the wall with the vent, using a long turn 90 at the wall when you go vertical."


    I'm curious about the "most of the time" and "above the flow line". I've got a layout with an elevation problem -- I'm about 60' from the septic tank, and there's not enough room to roll the 3x3x2 wye up to 45 degrees for the vent without the vent rising above the surface of the slab. I've tried to simulate the flat vent with a test line, water, toilet paper, and various solids, and have (so far) not seen any hint of hangups, clogging, etc., as the flow passes the vent opening (flow goes from initially filling the pipe to below the flat Y opening), so I'm cautiously optimistic that I can get by without the full 45 degree roll (or any roll at all, for that matter). I can live with occasional snaking of the vent if need be. The vent rises at 1/4" per foot. What's the real-world wisdom/experience on this? Is there any other obscure fitting that might allow a lower overall profile and get the vent opening up higher?

    (This fitting will be about 2 feet downstream from a Toto Drake feeding into a 4x3 reducing closet bend, fwiw).


  2. #2
    Plumber jimbo's Avatar
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    Default

    Well, you correctly described the reason for this requirement...to eliminate possible clogging of the vent. Your simple experiment did not simulate all the real world situations over many years. Now, would it work ok most of the time...possible occasional snaking of the vent as you mentioned..... I suppose. Would an inspector allow it....I doubt it.

  3. #3
    Plumber Winslow's Avatar
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    Quote Originally Posted by Mikey
    In another thread, Terry once said:

    "Fittings on their side (horizontal) and below grade should be wye fittings.

    When rolling a vent off with a wye, most of the time, you would use a 45 and make sure that the rolled vent is above the flow line of the waste line.
    For the toilet, that would be wye with 45 pointing the same direction as the pipe, and running toward the wall with the vent, using a long turn 90 at the wall when you go vertical."


    I'm curious about the "most of the time" and "above the flow line". I've got a layout with an elevation problem -- I'm about 60' from the septic tank, and there's not enough room to roll the 3x3x2 wye up to 45 degrees for the vent without the vent rising above the surface of the slab. I've tried to simulate the flat vent with a test line, water, toilet paper, and various solids, and have (so far) not seen any hint of hangups, clogging, etc., as the flow passes the vent opening (flow goes from initially filling the pipe to below the flat Y opening), so I'm cautiously optimistic that I can get by without the full 45 degree roll (or any roll at all, for that matter). I can live with occasional snaking of the vent if need be. The vent rises at 1/4" per foot. What's the real-world wisdom/experience on this? Is there any other obscure fitting that might allow a lower overall profile and get the vent opening up higher?

    (This fitting will be about 2 feet downstream from a Toto Drake feeding into a 4x3 reducing closet bend, fwiw).

    try rolling a fitting 1/16 bend into the san tee and see if you are still above the cement. You have to roll the tee or you will have vent clogging problems down the line. Water will back up into the flat vent even under normal flow conditions, Affluent in the wast water will eventually clog up the vent.

  4. #4
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default

    It's a wye, not a T, but I am going to see if there's a combination of fittings that might raise the vent line somehow, within the constraints I've got.

    That said, I fail to see the difference between a 2" drain line and a 2" vent line with respect to clearing itself, if they're both sloped at 1/4" per foot, which in another thread is described as the optimal slope for draining. Given the outflow characteristics of the toilet, I can't imagine the water lingering around long enough to back up into the vent. I do have a Plan B, though, just in case ...

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