Plan for 2nd Floor DWV

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by nelsonba, Sep 16, 2007.

  1. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    I'm planning to add a 2nd floor bathroom and I'm wondering if this plan is acceptable for the DWV system. If so, can it be simplified in any way?

    Thank you

    Attached Files:

  2. patrick88

    patrick88 Plumber

    Messages:
    836
    Location:
    Webster Ma.
    I think that looks good. You put alot of thought into that and did not make it complicated.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,280
    Location:
    Bothell, Washington
    That's pretty good.
    The toilet is the only fixture that doesn't need a trap, it's in the bowl itself. You would just 90 up to a closet flange.

    I like that you revented at the lav, into the downstairs vent at 42"
    I see a vent for the shower, good, you could also use 1.5" for the shower vent, and keep the 2" for the trap and waste. It is fine if you oversize the vent though too.
  4. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    A few more questions...

    1) Does it matter if the shower drain enters the main stack above or below the toilet drain?

    2) Does the shower vent horizontal run have to be 42" above the floor or just 6" above the trap wier?

    3) I'm in Minnesota. Can the horizontal shower vent run on the cold side of an exterior wall. (It's a knee wall). I was planning to attach it to the back of the studs.

    Thanks
  5. doesn't matter.
    technically, i think it must be 42" (or at least 6" above the sink rim) although it is true that the shower would show a problem first before the vent got used by sink waste water if the last part of their common drain got blocked.

    Q3. I don't know.


    I like your diagram too, as you managed to say it all in about ten lines and two squiggles. "Anything worth saying can be said in about ten words."


    David
  6. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    A few more questions…

    1) Does the p-trap for the shower need to be accessible? If so, would an access hole to the side of the shower be acceptable or do I need to have an access panel in the ceiling of the room below?

    2) I have 2x8 floor joists (full 8 inches). I will need to run the 2" shower drain through a few of them. The first horizontal run starting at the shower drain will be parallel to the joists and the other will be perpendicular. Any issues with this? My understanding is that you can drill holes up to 1/3 the total depth of the joist as long as you stay away from the top and bottom 2 inches of the joist.

    3) Will a 2" p-trap fit in a 2x8 joist space?

    3) The shower vent will run up through or directly behind the knee wall. Does anyone know if it can be run in the cold space?

    4) Same for the drain. Can it run through the joists on the cold side? I'm trying avoid drilling holes through the joists directly under the sole plate of the knee wall so it's easier to get at.

    Thanks!
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,258
    Location:
    New England
    There's no requirement to be able to access the trap for maintenance...once it is in, it is usually good until you decide to remodel. Doesn't hurt if is, but is not required.

    The vent can run through cold areas...it eventually goes outside. As long as there is slope to it, it should be fine.
  8. calif_pilot

    calif_pilot own a plumbing company

    Messages:
    11
    Location:
    Burbank California
    make sure you don't use a union type trap for the shower drain
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,020
    Location:
    Cave Creek, Arizona
    dwv

    That 3" line for the toilet is not the vent from the downstairs toilet/bathroom is it?
  10. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    Nope

    The 3" line will be a new line running down through a closet and connecting to the main stack in the basement. The existing main stack is vented separately.

    Can the drain from the shower run through a cold area?
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,020
    Location:
    Cave Creek, Arizona
    drain

    As long as the faucet is not dripping when it is cold.
  12. nelsonba

    nelsonba New Member

    Messages:
    116
    Location:
    Minnesota
    OK. So I'll run the drain to the knee wall, bring the vent up, and then turn it back towards the warm side before running it to the stack.

    Any limitations on turns? Can I do it with 90s, or should I use 45s?
  13. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND
    Weir of the trap has no bearing on horizontal venting height, only on distance of trap to vent, offsets before vent and tailpiece length. But on to what you meant.


    MN Plumbing Code: http://www.revisor.leg.state.mn.us/bin/getpub.php?pubtype=RULE_CHAP&year=current&chapter=4715



    While it is legal to run the shower vent horizontally 6" above the spill line of the shower, your connection into the 3" vent stack must accomodate the same requirement of the water closet (as the 3" is it's vent).

    Theoretically, it could be piped like this:


    [​IMG]


    But, if one really wanted to be a devil's advocate, it could be argued that if all of the following occurred at once,

    1: 3" stack below water closet plugged
    2: water closet trapway plugged
    3: shower trap plugged

    water from the lavatory and toilet could compromise the horizontal potions of the shower vent, bringing with it paper and maybe some floaters (lol) that could stay after the stoppages were taken care of.

    Now that is an extreme example that could probably only happen as a result of a fraternity prank, but it is possible. Just think if there was a waterproof partition that extended upwards from the lavatory! :eek:



    Thats why we just pipe the stuff at 42", too much thinking otherwise.

    Attached Files:

    Last edited: Oct 17, 2007
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