Vent distance question

Discussion in 'General Plumbing Help' started by odynefit, Dec 9, 2017.

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  1. Dec 9, 2017 #1

    odynefit

    odynefit

    odynefit

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    I'm installing a basement shower where a 2" drain for the shower is almost 8' from the 3" vent. Looking at the vent distance table, 2" drains should be no more than 8' away. Since i'm so close to the limit, is it recommended to install a 1 1/2" vent just for the shower vent, or if i carefully measure and calculate the slope is it reasonable to install a drain this far from the vent? There is a toilet next to the existing 3" vent.
     
  2. Dec 9, 2017 #2

    Zanne

    Zanne

    Zanne

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    In some places, a 2" drain trap arm has been reduced to only 6', but I don't know about your area. You could do a branch vent that goes up before the drain and tie the branch in to the existing vent farther down. The drain does not have to go down at the same place where the vent goes up-- it can go after it (but it can not go down before the vent).

    Diagrams/sketches and measurements would help in this situation so people can see what you are dealing with.
     
  3. Dec 9, 2017 #3

    odynefit

    odynefit

    odynefit

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    I've attached a diagram. There is a 3" pipe under the concrete and i don't know exactly where it is, but i can guess that it runs near the shower drain. I plan to dig up the concrete from the existing shower drain to the new location and tie in at the old location. its just under 8' (maybe 7' 10"). We follow the 2012 plumbing code.

    basement_drains.png
     
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  4. Dec 9, 2017 #4

    odynefit

    odynefit

    odynefit

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    here's a side view if this helps to explain it better... is the distance to the vent calculated on the 2" or 3" pipe?

    basement_drains2.png
     
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  5. Dec 10, 2017 #5

    Zanne

    Zanne

    Zanne

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    Maybe I'm dense, but on the second one, could you mark where the vent is? Does each fixture have it's own vent or will they be sharing a vent/wet venting?
     
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  6. Dec 10, 2017 #6

    odynefit

    odynefit

    odynefit

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    It is marked on the left side. It comes out of the concrete at 3" then a Wye with a clean out and a 2" vent to the roof. When calculating the distance, do I use the distance to the vertical vent, or can I use it as a wet vent and measure the distance from the 3" drain pipe under the concrete to the shower trap?
     
    Last edited: Dec 10, 2017
  7. Dec 10, 2017 #7

    Zanne

    Zanne

    Zanne

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    This diagram explains how to measure the trap arm (the slope is very important-- it must not be greater than or less than 1/4" per ft slope).
    [​IMG]

    Hmm.. a wye with a cleanout? Do you mean a wye is what connects the vertical to horizontal? Or is a wye being used on a vertical pipe with a cleanout?

    Am I correct in assuming that each of those fixtures currently have no independent vents and all tie in together at the vent? If so, they are wet-venting. I'd have to look up the IPC 2012 rules for went-venting (which I'll have to do later since I'm about to run to the store).

    One important factor is that the shower drain needs to tie in to the main drain above where the toilet hooks in. Otherwise the toilet water and gunk can get in to the shower drain line.

    If there is a nearby wall, you might want to do branch vents into that wall and then connect it to the main vent in the space above. One of the official plumbers could probably help you with a diagram.

    Frodo is very good at those.
     
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  8. Dec 11, 2017 #8

    odynefit

    odynefit

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    I attached a photo of the 3" that comes out of the concrete, wye, cleanout, and converts to a 2" to a vent. Hopefully that explains it much better than i could in words. Right now there is roughed in toilet and shower drains and a vent to the roof. The rest of the house's drains are on the other end of the house. The shower is down the drain from the toilet, but i should be able to tie in the shower drain to the 3" on the top of the drain pipe. I plan to move the existing roughed in shower drain 3' before installing the bathroom.

    So going back to my original question, do i calculate the distance from the shower drain to the 3" pipe in concrete (because its a wet vent), do i have to calculate it to the existing vent on the wall going up to the roof, or should i install a new vent near the shower drain and tie into the existing vent on the wall?

    thanks for all of your help!

    20171030_193109.jpg
     
    Last edited: Dec 11, 2017
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  9. Dec 13, 2017 #9

    Zanne

    Zanne

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    I honestly don't know. I'll have to defer to the experts on this but I think they are busy with the holidays.

    But, I am confused about what is going on there. Why is there a trap in that one spot with the smaller pipe sticking out the top? What is the open wye doing on that same pipe?

    The P-trap arm is too short-- that creates a crown vent. Should be at least 4" if it is actually serving a pipe.

    I could be wrong, and a real plumber can correct me if I am, but the cleanout thing looks weird. Why not remove the cleanout, move the 2" pipe over on top of it and use a 2" to 3" coupling/adapter to bridge them together and have the cleanout somewhere up higher on a sanitary tee? Or is that pipe coming down a drain pipe and not a vent? I'm so confused by this. LOL.
    If it is a drain pipe and not a vent, please ignore this suggestion in the sketch.

    plumbingforumsuggest1.png
     
  10. Dec 13, 2017 #10

    odynefit

    odynefit

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    All of this was here when i moved in. The small pipe is from a water softener. it flushes water a couple times a week into that trap. Not sure why the other wye is there. Maybe for a washing machine that could move there? I suspect this was added after the house was built since the PVC is a different color. Might have been added when the water softener was installed. I agree the trap arm isn't long enough.
     
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  11. Dec 14, 2017 #11

    Zanne

    Zanne

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    I'll see if I can flag someone down on one of the sister forums to see if they can help out since I don't want to steer you wrong.
     

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