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Thread: Wet Vent a tub through lav drain?

  1. #1

    Post Wet Vent a tub through lav drain?

    Is this acceptable?

    I have a lavatory that drains via a 2" x 2" x 1-1/2" sanitary tee. the 1-1/2 goes up to vent, the 2" goes down to the floor, travels to a stall shower where it is converted to 3" and then the shower stall is drained. Just after the shower is collected, there is another 2" vent. Can I drain a bathtub into the 2" portion between the sink and the shower, and use the sinks vent as a wet vent? The sink is about 5' from where the tub drain would enter. This is all new construction, but because of windows and other factors it is difficult to get a vent to the tub.

    Also I was thinking of combining all the vents in the attic into a 3" horizontal and running them over to an existing 3" vent. The horizontal run would be about 30' ~ 35' is that too long? I'd rather no poke another hole in the roof.

    Regards,
    Greg

  2. #2
    Plumber Deb's Avatar
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    Default Deb

    Wet vents have some pretty specific rules and that would not meet UPC code for a couple of reasons (you could be under a code with different rules that allows this. This difference in rules is one of the reasons that makes it tough to give advise remotely).
    However, you mention that there is a another 2" vent after the shower tie in. If this is actually a vent (since this is new contruction and this vent doesn't seem to be serving anything, I am curious why it is there and if it is actually a vent), you can most likely use this to vent your tub. Keep in mind trap arm length maximums.
    If you are doing this plumbing yourself, it may be in your best interest to call a plumber for some consultation. We see everything out there in the real working world (which can be very different from the world code is based on) and can usually find a solution for most problems and still meet code requirements.
    Deb
    The Pipewench

  3. #3
    Plumber Deb's Avatar
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    Default Deb

    Forgot to answer the vent question. Yes, you can run a 3" vent that far horizontally. Be sure to support the horizontal runs every 4', maintain grade, and make sure that there are no bellies, sags, or low spots for rain water and condensation to collect.
    Deb
    The Pipewench

  4. #4
    DIY Senior Member e-plumber's Avatar
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    Arrow Wet Vent

    >>>>>> 2" x 2" x 1-1/2" sanitary tee <<<<<<

    The problem I see right away would be this fitting. The vent should remain full 2", 1-1/2" would not be acceptable and would fail a roughing inspection.
    e-plumber

  5. #5

    Question

    First, Thanks for everyones help.

    As far as the vent remaining a full 2". I looked in a CodeCheck plumbing book, and it says that fixtures at different levels (same floor) may share a vent, but the vertical drain between the fixtures is a wet vent and must be min of 2", the common vent is sized per fixture units of upper drain, in the diagram it shows a 1-1/2" drain and a 2" drain dumping into a 2" 'stack', then above the top drain, the 1-1/2" the vent is 1-1/4". This is very similar to what I would Like to do except that there is no horizontal piece between the two drains, in their diagram.

    The 2" vent just after the shower drain is a vent for the shower, the distance is too far from the lavatory to try and share that vent.

    I will look tonight to see if I can get a line from the tub over to the shower to share that vent, but if I can't I still wonder if I can share the lav vent? The book isn't real clear with this setup.

    Here is another question, I know you can't use sanitary tee's on their back for drains, but this is what I would like to do: for the toilet come from the flange to a closet 90, run about 2' to a 3"x3"x2" sanitary tee on its back to vent the toilet, then continue about 30 feet to the area wher it ties with other drains. The reason I would like to use a sanitary tee is to gain the clearance needed for proper pitch. If I use a wye and a 45 I will have to drop that end of the pipe quite a bit. With the sanitary tee, I can keep it up close to the floor on that end. I understand why with drains you wouldn't want a tee, but how about just a vent?

    Thanks again.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default vent

    It will not pass inspection in most areas, because anything below the "flood" rim of the fixture is considered a sanitary drain, and you cannot use a tee in a horizontal line in a drainage pipe..

  7. #7

    Default

    OK, I guess I'll use a wye. I can put it on a 45 degree angle right. Also I read that all the vent fittings should point toward the trap that they service. But wouldn't it be better for the the wye to point toward the drain side like below. I imagine it is the same if the toilet were a shower or some other fixture. Which way should it point?




    Thanks

  8. #8
    DIY Senior Member e-plumber's Avatar
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    Exclamation Correct Direction of Fitting

    The sketch depicts the correct way a vent fitting *should be installed. We are permitted to use a tee-wye, 45's and regular 90's in this scenario, (not for wet venting of course). It can help when the area where you're working is very tight.

    *An easy way to remember which direction the vent fitting should be is to visualize water flowing down the vent pipe, it must flow in the same direction as the drain.
    e-plumber

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