New construction DWV system

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by MushCreek, Apr 30, 2013.

  1. MushCreek

    MushCreek New Member

    Messages:
    34
    Location:
    Travelers Rest SC
    Hi! New guy here. There seem to be plenty of experts on this forum, and I'm hoping I can get a review on my DWV for a new house I'm building. I'm way past DYI; I'll tackle anything. I have 3 books on plumbing, and they all seem to differ. The local inspectors just give things a quick glance, so I'm more worried about having a properly operating system than passing inspection. I did a crude sketch, then assembled it dry-fit to see how it's all going to go together. I attached the sketch and a couple pics which give a 3D perspective. A few points:

    Every fixture is on its own branch and has its own vent, which will then tie together in the attic.
    This is for a master bath and a powder room in a one BR house.
    The main branch is 3"; the smaller branches and all vents are 2".
    The whole thing drops into the basement through a sanitary T (horizontal to vertical).
    This main stack goes up through the attic as the main vent.
    There is a bathroom in the basement (below the powder room) which was plumbed by a licensed plumber, so I assume (!) it's right.
    The little arrows on the sketch represent clean-outs.
    The main branch will be below the floor joists. I connected the 2" branches with a Y+1/8 rolled up on a 45 degree angle to tuck the 2" stuff up between the joists.

    I have a few questions, but first let's see if I'm in the right ballpark with this thing. I already know all of the basics, such as pitch on the horizontal runs, and which kind of fittings are allowed where. I'm more concerned about the function of the whole system.

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  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    Here, we could not install "flat vents", and the cleanouts would be accessible above the floor, rather than in a crawl space. You also did not have to "roll" the combos upwards.
  3. asktom

    asktom Member

    Messages:
    557
    Location:
    Victor, MT
    The san tees on their backs should be combinations. The combination used as a closet bend on the toilet could be a 1/4 bend. The shower drain looks very cheesy, it isn't the correct one for either tile or a pre-fab.
  4. MushCreek

    MushCreek New Member

    Messages:
    34
    Location:
    Travelers Rest SC
    What is a 'flat vent'? I can correct pretty much anything at this point. Do you mean the one for the shower?

    The clean-outs are in the basement, not a crawl space. Should I add a clean-out for the toilet that doesn't have one? It's too close to the wall to go straight back, but I could add a Y downstream for a clean-out.

    I don't understand what san tees 'on their backs' that you are talking about. There are two 3X3X2 san tees used for vents only. Is a san tee not OK for a vent? The fittings for the shower, washer, and lav are all Y+1/8 combination. I rolled the combos upward so they would tuck in between the joists- the main branch hangs below the joists. Again, this is in a basement, so the less hanging down, the better. I used a combo on the master toilet to accommodate a clean-out- not necessary?

    That shower drain is just one I had laying around; I used it for illustration purposes. I'll get a proper tile drain.

    Another question- the san tee for the powder room toilet vent is at a 45. Should I go vertical, then across with a 90 ell?

    I appreciate the help- DWV is more complicated than I first thought!
  5. asktom

    asktom Member

    Messages:
    557
    Location:
    Victor, MT
    Yes, it is the shower that is flat vented. It would be much better if it was configured more like the lavatory in the bathroom.

    You don't need a clean-out on the other toilet, the one at the end of the line works for it.

    Yes, the 3X2 san tees should be combinations (also the 2" on the shower as shown). Rather than give a long-winded complicated explanation I will cut to the chase and say they can't be used in that position until they are 42" above the finished floor. Rolling the combinations upward is OK, but not required. The combination on the toilet is not necessary, a long sweep 1/4 is fine - again the end of line cleanout covers it.

    Glad you aren't using that shower drain.

    The toilet vent at a 45 is the correct way (except it should be a combination, not a san tee). If you go straight up and 90 to the wall you have created a flat vent. The thing about flat vents is if the drain backs up that type of vent can clog and remain clogged even when the drain is cleared. A clogged vent can create stinky, subtle problems. For that reason they are bad practice &/or illegal depending on the situation and local codes.
  6. MushCreek

    MushCreek New Member

    Messages:
    34
    Location:
    Travelers Rest SC
    Hmmm- don't know how I'm going to avoid having part of that shower vent flat. I can go up from the shower branch, with a combination, but then will have to go horizontal to reach a wall to turn the vent vertical. From the drain to the center of the stud wall is about 21". The powder room toilet is much the same way- I have to travel about 24" to hit the wall. As shown, the powder room toilet is rolled at 45 degrees, then goes flat over to the wall where a 90 ell will turn it vertical. I know with a sink the vent can't go horizontal until 6" above flood level, but how do you do that under a shower? I guess I could make sure the drain line runs under a wall that I can shoot a vent up through.

    As for the san tee being used for venting- I've seen it done many times. There's a good tutorial from Oregon that is referred to on this forum, and you can see san tees being used that way under the floor. I know you can't use one for drainage unless they are mounted vertically. I don't mind using combis; I'm just trying to learn.
  7. MushCreek

    MushCreek New Member

    Messages:
    34
    Location:
    Travelers Rest SC
    Okay, here's the work-around I came up with for the shower vent. I basically re-routed the drain under a wet wall so I could go vertical with the vent. I also swapped out the sanitary T's for combi fittings for the two WC vents. I shifted the powder room branch over so that the vent could up on a 45 degree angle and not have to go flat to reach a wet wall. Now I'm trying to decide whether to keep the other branches tucked up between the joists or not. If I do, the clean-outs will get buried when I finish the ceiling.

    [​IMG]
  8. asktom

    asktom Member

    Messages:
    557
    Location:
    Victor, MT
    The shower set-up looks better.

    As for the combinations rather than san tees, I base my advice on the Uniform Plumbing Code as it was interpreted and enforced in Southern California where I learned plumbing. There are other codes and the UPC is modifed and interpreted differently in different jurisdictions (and by different inspectors). My opinion is based on UPC 905.3 which reads, "... vents less than six (6) inches (152mm) above the flood level rim of the fixture shall be installed with approved drainage fittings, material and grade to the drain."
  9. MushCreek

    MushCreek New Member

    Messages:
    34
    Location:
    Travelers Rest SC
    Yeah, I did a lot of googling about the vent fittings this AM, and the findings were inconclusive at best. We're under IPC 2006 here, and I think they're allowed, but the combi is a little better I think. At least I know it's more than adequate.
  10. asktom

    asktom Member

    Messages:
    557
    Location:
    Victor, MT
    I forgot to mention that all those dry fits may well mess you up. The fittings have a tapered socket and when they are slimed up with glue the pipe will push in farther than when things are dry. Expect the pieces you cut to all be too short.
  11. MushCreek

    MushCreek New Member

    Messages:
    34
    Location:
    Travelers Rest SC
    I know that. I measure the actual distance between fittings and add the socket depth(s). The dry fit is 'too long' as shown. The branches are intentionally left long for final fit. Since none of the interior walls are built yet, I have flexibility on location, as well. Being a toolmaker by trade, though, I'll insist that everything match the drawings! Everything about building a house takes me longer than it should due to my obsession with accuracy. Thanks for the heads-up!
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