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Thread: Plan for 2nd Floor DWV

  1. #1
    DIY Senior Member nelsonba's Avatar
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    Default Plan for 2nd Floor DWV

    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
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    Plumber patrick88's Avatar
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    I think that looks good. You put alot of thought into that and did not make it complicated.
    I'm just starting to work with an old friend of mine to bring solar electric and hot water systems, wind turbines, Flex Fuel Boilers, batteries, hydroponic gardening, books, pellet grills and more. Also the parts for DIY installation.

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    Forum Admin, Expert Plumber Terry's Avatar
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    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. #4
    DIY Senior Member nelsonba's Avatar
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    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. #5
    Homeowner geniescience's Avatar
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    Quote Originally Posted by nelsonba
    .... 1) ... shower drain ...above or below the toilet drain?
    ...
    doesn't matter.
    Quote Originally Posted by nelsonba
    2) Does the shower vent horizontal run have to be 42" above the floor or just 6" above the trap wier? ....
    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

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    DIY Senior Member nelsonba's Avatar
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    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. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #8
    own a plumbing company calif_pilot's Avatar
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    make sure you don't use a union type trap for the shower drain

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default dwv

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

  10. #10
    DIY Senior Member nelsonba's Avatar
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    Default 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. #11
    Moderator & Master Plumber hj's Avatar
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    Default drain

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

  12. #12
    DIY Senior Member nelsonba's Avatar
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    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. #13
    Plumber/Gasfitter dubldare's Avatar
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    Quote Originally Posted by nelsonba
    A few more questions...

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

    Thanks
    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/b...t&chapter=4715


    4715.2540 VENT GRADES AND CONNECTIONS.

    Subpart 1. Vent grade. All vent and branch vent pipes
    shall be so graded and connected as to drain back to a soil or
    waste pipe by gravity.

    Subp. 2. Vertical rise. Where vent pipes connect to a
    horizontal soil or waste pipe, the vent shall be taken off above
    the center line of the pipe. The vent pipe shall rise
    vertically, or at an angle not more than 45 degrees from the
    vertical, to a point at least six inches above flood-level rim
    of the fixture it is venting, before offsetting horizontally
    or
    before connecting to the branch vent.

    Subp. 3. Height above fixtures. A connection between a
    vent pipe and a vent stack or stack-vent shall be made at least
    six inches above the flood-level rim of the highest fixture
    served by the vent
    . Horizontal vent pipes forming branch vents,
    relief vents, or loop vents shall be at least six inches above
    the flood-level rim of the highest fixture served.

    STAT AUTH: MS s 326.37 to 326.45
    Current as of 07/31/07

    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:





    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!



    Thats why we just pipe the stuff at 42", too much thinking otherwise.
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    Last edited by dubldare; 10-17-2007 at 05:46 PM.
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