Venting under slab in basement, see my layout, where to add?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by joesloppy, Aug 16, 2005.

  1. joesloppy

    joesloppy New Member

    Messages:
    4
    Location:
    Sioux City, IA
    I am adding a bathroom in my basement complete with toilet, tub,
    shower, and sink. I believe I have the drainage system down but I
    don't quite have the venting figured out. I bought a book with about
    10 full color pages on how to vent plumbing properly but I still am
    having trouble figuring out what I need to do exactly. If you open the
    pdf or jpeg at http://www.kcengineer.com/piping.jpg or
    http://www.kcengineer.com/piping.pdf you will see my current layout. I
    have added letters to the pipes to aid in telling me where to come off
    for vents. If I understand correctly, I would only need to add a vent
    to the pipe labeled C which is between the shower trap and wye for the
    tub. Doing that I assume would allow the shower, tub, and toilet to
    pull air from that vent and not suck water out of a traps. The sink
    will have a mechanical vent you can buy for about $5, so this I assume would take care of both sides of the 4x4x2 double wye. Then again, maybe
    I don't need any vents as I did run 4 inch all the way to the toilet
    and 2 inch all the way to each fixture so the pipe may just vent itself
    because the top half would never be full. I am confused as what to do;
    this is my only option for layout of piping because of space
    restriction. By the way, the longest pipe is D, about 7' long. The
    rest are all 3' or less sections. Thanks for any advice! Oh, by the way, I looked at the toilet, tub and sink drain lines on the first floor to see how it was vented but I didn't notice any vents, probably because all run directly to the vertical stack by themselves and are vented by the stack which runs to the roof.
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,129
    Location:
    Bothell, Washington
    First off, very nice looking drawing.

    There are a few things to change though.

    I hired a plumber from Iowa that would have plumbed the basement like yours.
    I couldn't let him do any waste and vent layout in the Seattle area.
    We were using the UPC code, which I believe Iowa does too. I couldn't see any awareness on his part that he had ever used it.
    Every trap should be vented, and you can't use the stack from the upstairs plumbing for your vent.
    If your stack has plumbing waste from upstairs coming down it, it's not a vent.
    When you lay the waste line on the horizontal and run other waste lines in, they're not vented either.
    If you had a vertical vent stack, you could get a two way or three way fitting and run that many fixtures in, if they combine at the same level.
    You can't just branch off and add fixtures as you go.

    Fittings that are on their side must be wye fittings, not santees.

    Below is a drawing that shows two bathrooms with venting that are stacked.
    You will see from the drawing, that one vent through the roof will suffice, if everything is tied back together.

    [​IMG]
    Last edited: Aug 16, 2005
  3. joesloppy

    joesloppy New Member

    Messages:
    4
    Location:
    Sioux City, IA
    How about this, check out my actual layout here at http://www.kcengineer.com/pipingplan.pdf and see where I have everything. This sketch at http://www.kcengineer.com/pipingplansketch.pdf is how I thought to layout out the piping. I was going to use a regular wye fitting off of the horizontal run of the stack to go to the fixtures but then as you can see in the sketch where I have access, I have to 45 back around to get to the toilet, so instead I bought a Long Turn Wye, its really a wye that ends in a 90 with a 45 on that (mcmaster.com #2389K51). This will probably give you a better idea of whats going on here and my limitations with space. Thanks
    Last edited: Aug 16, 2005
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,129
    Location:
    Bothell, Washington
    With that drawing, it looks like you have plenty of room to add all of the vents.
    The vents would be in the wall using fixture fittings on their back. Since you are using PVC pipe and fittings, sizing would be like this.
    You would vent the:
    tub, 1.5"
    shower, 1.5"
    lav, 1.5"
    toilet, 2"

    All of these vents can be tied together into the 2" of the toilet and then reconnected to the vent on the second floor at 42" above the floor.

    http://www.iapmo.org/common/ROP2004/upc04rop/preprint/ch9.pdf
  5. plumguy

    plumguy New Member

    Messages:
    192
    Location:
    MA
    I would look in you're book under wet venting, because it certainly would be the easiest way to vent the whole bath. Of course it also depends on how far down(depth) the 4" is from the floor.
  6. Terry

    Terry Administrator Staff Member

    Messages:
    15,129
    Location:
    Bothell, Washington
    If he's going to do wet venting, he first must determine if the 4" line is the waste line for the upstairs.
    If it is, then no portion of the 4" will work for wet venting.
  7. plumguy

    plumguy New Member

    Messages:
    192
    Location:
    MA
    Well that shows you the difference in codes around the country! I think!?

    I would imagine and hope that the 4" is the... or at least one of the main drains for the house! Why would it matter if the bath was wet vented or if the fixtures were all individually vented!! As long as the 2" vent ties into a vent wether he has a future vent,existing vent or if not then would have to run the pipe up to another level until one is found that he can tie into 6" above the flood level rim of the highest fixture.
    Last edited: Aug 16, 2005
  8. Terry

    Terry Administrator Staff Member

    Messages:
    15,129
    Location:
    Bothell, Washington
    Maybe we're not taking apples and apples.
    Most codes I know of only allow wet venting for the same floor fixtures.

    Is that what you're saying?
    What he seemed to be saying was that the four inch from above would be the vent. I'm not aware of a code that would allow that.

    If he means to wet vent the lav over the tub vent, that would work. Where I'm from, that would be off the vertical 2" and it could be trap armed over to the lav.

    [​IMG]
  9. plumguy

    plumguy New Member

    Messages:
    192
    Location:
    MA
    What I was saying was instead of individually venting all the fixtures, it would be easier to wet vent the whole bath. Since he has 3 floor mounted fixtures which is the only type fixture you can wet vent(here), and yes they all have to be on the same level for it to work.

    But, regardless of how it is vented he then must get that 2" vent above the other bath like we both previously stated and then tie in or penetrate the roof.

    I would like to think that tying a vent into a main drain with drains rolling over it would be a no no...no matter where you go! Or at least we hope!!
  10. joesloppy

    joesloppy New Member

    Messages:
    4
    Location:
    Sioux City, IA
    OK, I think I got it, so here are some pics of the actually plumbing, I got a head of myself and will have to cut in and add some vents but you'll get the idea.

    http://www.kcengineer.com/b1.jpg
    http://www.kcengineer.com/b3.jpg

    The 2x4 on the floor in the picture represents the baseplate of the new walls. From what I am understanding, I have to buy a 4x4x2 reducing Tee and put that right after the elbow in the toilet line pointing up into the new wall so that is vented. Then for the long 2" tub line, I will add a WYE into that line near the trap and WYE up slightly into the boxed out area where the trap is and elbow over then up into the wall for another vent. The sink will also have a vent in its line which is the only line I have not run yet. I am wondering why though I would need to vent the shower line also as it will be off of a vented tub line. I guess I would have to think of it as if the tub is full and draining, where would the shower vent, although it only has about 4 feet to go till it hits the 4" toilet line that is vented. I can see the safest thing to do is vent every line which I was avoiding, but I would rather be safe than sorry later on. The stack I am coming from is the waste stack (upstairs toilet, sinks, tub all tee into it). So as you can see in the pictures I labeled everything, there is no "vent only stack" so I can not tie these new vent lines into anything. I would have to run a new line to the roof. That doesn't sound fun, so how about I do this:

    http://www.oatey.com/aav_public/why_vent.html

    Would bringing them all together into a 2" line connected to the 20 DFU sure vent work just as well. Its a roof-less system and later on if I have the 20 DFU model, I could add a washering maching vent and laundry sink vent to this basement venting system. Thanks for all the help so far. I am more confident that I am doing this right with this advice.
    Last edited: Aug 17, 2005
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