DWV Layout for Bathroom Remodel

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Stu27, Sep 15, 2010.

  1. Stu27

    Stu27 New Member

    Sep 15, 2010
    Northern Virginia
    I just started my master bathroom remodel. I am an experienced DIYer, but have no experience with DWV design or code.

    The remodel includes relocation of all three fixtures. I've attached a drawing of the current as-built configuration of the three fixtures and DWV layout. I'm not sure the original as-built DWV design meets code and wish to correct any deficiencies, if any, during the remodel (i.e. should the 1.5" bath drain be upgraded to 2" drain, was the bath vented adequately?…I recall it drained slowly).

    Also attached is a drawing of the new fixture locations. This drawing includes my attempt at an initial DWV layout. My thoughts are to locate the new sink drain in a half height false wall to keep the pipes in a heated space this side of the attic wall and to vent the new sink into an existing 3 inch vent stack (not shown) about 2 feet on the other side of the attic wall. I shortened the shower drain routing as compared to the previous tub routing, but the vent is still pretty far away from the trap… not sure what is acceptable here… if the shower trap needs to be closer to the vent, then routing from shower drain horizontally to the right (in the drawing) is an option to shorten the distance from drain to vent.

    The new toilet location seems to present a challenge in getting the wc flange in the desired location (for me anyway). I'd prefer to toilet be centered between the left-side finished wall and the new right-side cabinet. I have not been able to figure out a tie-in to the existing waste pipe that allows the wc flange to be located in the ideal position, currently I have about a 2 inch offset.

    Looking forward to the forum's advice on how to tackle the DWV design and also how to get that wc flange in the ideal spot to keep the toilet centered.


    dwv_layout_1.jpg as_built.jpg
  2. Stu27

    Stu27 New Member

    Sep 15, 2010
    Northern Virginia
    Could someone please answer these questions regarding my existing as-built layout (second drawing)?

    I've read a bunch here -- somewhere I think I read that tubs get 2" drains (is that required or preferred?) and that a trap arm should be no more than x feet from the vertical vent pipe. Is the tub vented correctly? Can you tell me if the the 1-1/2" tub drain meets code (Virginia)? The current distance from tub trap arm to the vertical vent pipe, traced down the drain pipe, is about 14 feet -- does this meet code?
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  4. geniescience

    geniescience Homeowner

    Nov 27, 2005
    humid summers hot, humid winters cold
    The elevation drawing (cross section A-A) showed venting for the lav sink in the "before" setup. Now you need to show it for the new lav location. A new cross section / elevation drawing. Mentioning "an existing 3 inch vent stack (not shown) about 2 feet on the other side" is not good enough; it needs to be seen (how you connect). Once that lav is connected to venting, you will have in so doing also vented the shower drain. This concept is the same as b.t.w. previously the tub drain getting its venting from the connection point with the vented lav drain; this may be news to you since you mentioned 14' but that is the distance to the second vent not the first one, a wet vent. This makes the distance about half of what you thought it was.

    your drawings haven't shown any long sweeps; all turns look tight.

    the WC connection is a subject that can be dealt with later

    in general, there are too many questions raised in your posts above. Pick your focus and stay on focus. New threads can be opened for new questions.
  5. Stu27

    Stu27 New Member

    Sep 15, 2010
    Northern Virginia
    Focus. Got it. I'll keep questions on point. I'm new to forums… this thread was my second ever. Please ignore the proposed new layout drawing. I will put another together with the attic vent tie-in properly diagramed. Gotta get into the attic tonight to get some location dimensions for the existing 3" vent stack…

    I assume it's okay to keep this thread open and by ask a few questions about the "before" setup -- I'd like to make sure I understand the venting...

    - the toilet is dry vented at the 2" vertical vent stack (which is about 5 feet from the toilet flange as measured along the toilet drain).

    - the lav is dry vented with a vertical vent at the lav trap (the vent is about 6" from the trap weir which is > 2D) and the lav vent then ties into the 2" vertical vent stack with a horizontal run that is 42" above the floor (which is more than 6" above the flood rim of the lav -- the highest fixture on this vent branch).

    - the tub is wet vented. There are two wye's along the 1-1/2" tub drain: the first is the lav drain and the second is the toilet drain. Is the lav drain considered the wet vent for the tub or is the toilet drain? Aren't both the lav and toilet drains helping the tub wet vent, but only one is probably used in a developed length calc?

    Did I get all that right? Or any of it?
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