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  • Sep 1, 2010, 07:30 AM
    DWV layout in two fixture bathroom, slab floor...
    Hi All, I'm new here and am hoping for a little help in plumbing in the DWV for a two fixture bathroom, WC and Lav. The floor is concrete slab and I'm hoping to minimize the amount of removal necessary to plumb in the waste lines. I'm located in Northern Calif. if that helps with code requirements.

    I'm going to try and attach the bathroom layout plan, any help/diagram of how I might lay out the drain and vents would be much appreciated. Thank you, Mike

  • Sep 2, 2010, 04:36 AM

    Hi Mjwallace...

    Can you tell us if wet venting is allowed in your area? If I remember, seems wet venting is allowed in some of California.

    Milo Dolezal (another "plumbing expert") is a plumber from your state and will know the answer to my question above. If he sees this he may pop in and run with this one. If he is unavailable please answer my question and I'll try to draw something up in the next day or so... OK?

  • Sep 2, 2010, 07:16 AM
    Hi Mark,

    Thanks for the reply. I suspect, though I'm not certain, that wet venting is not allowed here in Sonoma County, Calif. I think we adopt the strictest building codes.

    I've added a drawing with a layout I think will work out. I would appreciate your input.

    We have demoed the concrete slab over to where the existing toilet was located and removed the existing 4" iron drain pipe to replace with 4" ABS to septic tank. Lav drain, 1-1/2", will run horizontally through wall then drop through sole plate into trench and tie into 4" line downhill from toilet.

    Vent up wall behind toilet will be 2" and vent from lav, 1-1/2", will run horizontal and tie into 2" somewhere above 48" from floor.

    How about cleanouts? One in drain line below lav stub out, but what about for the toilet?

    Thanks for your help!
    (Why can't I imbed an image? I must be doing something wrong)
  • Sep 2, 2010, 07:24 AM
    Ooops... I linked to the wrong picture above and can't seem to edit the post.

    Here's the one I meant to link to:

  • Sep 3, 2010, 04:10 AM

    Hi Mike...

    Couple more questions and then we'll finish this up... OK?

    Where is this bathroom going... what kind of building/application?

    Any other bathrooms in this "unit" or building?

    Is there a 3 or 4" vent associated with this unit/building that already penetrates the roof?

    Let me know and I'll finalize my answer when I get back in fro work tonight.

  • Sep 3, 2010, 07:32 AM
    Hi Mark,
    Thanks again for your input. The bathroom is located in a light commercial building in an agriculture zoned area of Sonoma County. The property was originally developed as a chicken laying facility but has since been used for a bee keeping and honey production plant and probably various other uses through the years.

    The building that the bathroom is located in will be used as an office. There are no other bathrooms in the building. The new drain line will be also serve a sink in an adjacent break room... something I discovered yesterday when completing the slab demo.

    There is no 3" or 4" vent penetration at the roof. The sink in the break room has a 2" vent, iron pipe, that serves only the sink. The original toilet and sink, now removed, had a separate 2" vent that penetrated the roof. The wall that the original bathroom plumbing was located in, supply and DWV, has been removed to enlarge the bathroom and accommodate ADA requirements.

    I'm attaching a revised drawing with the existing break room sink drain and vent location.

    Existing vents and my proposed vents are represented by red dots.

    Thanks again, Mike
  • Sep 4, 2010, 07:36 AM
    1 Attachment(s)

    Hi Mike...

    Your drawing looked pretty good... may work fine for you. Read on and apply what you need.

    In any commercial application you'll need to penetrate the roof with a 4" vent (3" if you only have 3" underground) if there is no other 3 or 4" vent through the roof in the building. You'll need to check with a plumbing inspector in your area to see if this is required for your job.

    I drew this using 4" as a requirement.

    For the toilet use a 4" long sweep elbow as I drew it up, or if you have the room, a wye and street 45 (or combo wye) like you have drawn. Then, come out of the ground with 4" and install a 4" cleanout that should be rotated away from the bathroom so it can be readily accessed from the other room should the main line clog up. The cleanout needs to be full size 4" here.

    You need a 4" long sweep elbow for the horizontal to horizontal change of direction.

    Come out of the ground with 2" long sweep elbows for the lavatory and the other sink. Install cleanouts on the sink drains.

    All vents connect into the 4" at 48" off the floor for the toilet and lavatory vent and up in the ceiling for the other sink vent. The lavatory drain should run over 1.5", but no need to loop the vent back as the vertical lavatory drain/vent is within 3-4 feet of the drain and will not require the vent to loop back.

    Let me know if all this makes sense... OK?

  • Sep 4, 2010, 09:17 PM
    Hi Mark,

    Thanks again for all your input and help with this project. Your drawing makes good sense to me but I have a couple more questions.

    I've attached a quickie ISO drawing of what I think your plan would look like plumbed in... did I get it correct?

    I'm not sure of the locations you suggest for the clean outs. Could you mark up my ISO and repost it for me showing what you suggest?

    If I was to put a 4" two-way clean out just outside the building in the drain line could I eliminate the 4" clean out in the wall? I'm just trying to eliminate having to open up the wall in the adjacent room.

    On the lav clean-out, could I install it directly below the drain, rather than over by the toilet, and run the entire drain line in 2" rather than 1-1/2". Again I'm just trying to eliminate having to have a cleanout cover on the wall next to the toilet.

    Thanks again,
  • Sep 4, 2010, 09:22 PM
    Comment on MJWallace's post
    Yikes... I forgot to resize my drawing before submitting it. Let me know If you need me to shrink it up and repost. Thanks, Mike
  • Sep 5, 2010, 02:12 PM

    Mike, the size is fine. Looks like you understood perfect!

    Code calls for a one way cleanout at the front of the building... not usually accepted for two ways as you can image how awful it would be if someone was snaking the drain line while someone was on the toilet... *OUCH*.

    The two way cleanout at the 4" inside by the toilet could go inside the wall...should just need to install an access cover plate so it can be removed to access the cleanout. The access cover can be in the other room behind this room...just face the cleanout that way.

    For the sinks, If you run 2" over and install two way cleanout right at the sink and then go up with the vent there... that would work well, too!

    You decide... :)


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