DWV Hi Rise - WC-dedicated Soil Pipe max length and venting question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by tomahawk9, Aug 9, 2010.

  1. tomahawk9

    tomahawk9 New Member

    Oct 13, 2008
    hi all.
    On 22nd floor of 29 story building.
    15 year old building
    Plumbing was done hap hazardly to say the least. Emerging Market Stuff.
    I am trying to remediate two vent problems which are both above me and below me.
    Both relate to Vent lines serving a Lav and a WC with Drops and Sags (major Like 1.5 feet).
    Also the Wyes into the WC Vent are backwards facing downstream...
    Every apt in this zone that i have been able to access has this bad venting or some variation of it....

    Four files attached
    2 "schemes of what is really there"
    2 "bathroom blue print plans" dont pay too much attention to those (backward fittings etc.
    they are not really accurate and also dont plan the WC vent which is very much wrongly there with a backwards wye to boot (I flipped the wye in my my schematic).
    So these saggy vent pipes are being ejected with poop from a backwacks wye to boot!

    Both bathrooms have the same problem of Vents lines (of 22F lav connect to 23F WC) with a major major drop of some 1.5 feet.

    ***Key questions
    1) because soil pipe is a dedicated soil pipe and has auxiliary and relief vents on the way up and down, do i even need these drains to be vented (????) or will the Soil Pipe Stack provide enough relief to move the packages provided there is enough (but not too much) slope? and confirming the aux vents.

    If every other apt is also plumbed like this I know the vents are already a mess.

    ***2) Do the building vent stacks need to be replaced if they are literally full of it?

    Kids bathroom
    Cant be vented from within 2 feet of the as ideal trap there is too much concrete in the way.
    Would require either moving the toilet in all 29 apartments or...
    ...some how running a vent through the floor cutting through a 12 inch slab and redoing 29 showers.
    It's just a stupid design on the bathroom.
    ***3) At point *** in the "kids bathroom Scheme" which is 7.8 feet from the bottom of the 90 degree Bend (that is the trap weir correct?) it might be possible to run a rising horizontal slab with a wye rolled to 45 with a quarter turn to run its straight to the vent. Maybe....

    Master vent can be re-piped, if advisable, but it will be invasive and i would want to do it as far from the trap weir as I could in order to make it easy to put in the combination Y-1/8 and then turn it another 45 to hit the Vent Stack. \
    ***4) Do I need to vent that WC - dedicated soil pipe as it goes into a dedicated waste line. If yes can i stretch it out to say 8-9.5 feet around the corner to make it easier to get a rising tie in to the Vent?

    Any thoughts, code support and practical experience appreciated.
    Going to be a major job dealing with cutting out all the ceiling boards and Stack cut ins etc...

    I have pictures...if anyone really wants... but its a mess up there pipes going everywhere....

    From Thailand....

    Kids Bathroom Original.jpg MASTER2.jpg View attachment 11187 View attachment 11188

    Attached Files:

  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    1. I have absolutely no idea of what your are trying to depict.
    2. IF the system is acutally bell and spigot fittings as depicted, then it is almost IMPOSSIBLE to install the backwards.
    3. I doubt that ANY pipe could "sag" 18" without breaking. That distance is more of an offset than a sag.
    4. You appear to have a "bit of knowledge", but may not have enough to really be diagnosing this system, since little of what you indicate should happen in real life. Pictures would be more helpful than drawings, because they will tell us WHAT things look like, rather than what they SHOULD look like.
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  4. tomahawk9

    tomahawk9 New Member

    Oct 13, 2008
    Pictures of : DWV Hi Rise - WC-dedicated Soil Pipe max length and venting question

    P1000075.jpg CIMG2769-1.jpg CIMG3255_2.jpg View attachment 11195 View attachment 11196 View attachment 11197
    Thx for your response
    1. ok, i will try to help you see what I see.
    2. its not bell and spigot. but that was the easiest way for me to depict it.
    3. yes vertical offset drop like picture three. that is the vent branch pipe serving the Lav and the WC.
    4. This is not america. this is amazing thailand. you would be surprised what can happen in real life.

    I know enough to know that "a vent branch should be free of drops and sags and each vent shall be so graded and connected that as to drip back by gravity to the drainage pipe it serves." and I know that these vent branches dont meet that code.

    What I am trying to find out is what to do about it and whether the WC needs the vent or how far down the run i can place a properly sloped vent given the soil branch is connected (at a rather long distance) into a dedicated soil pipe that is itself vented.

    kids bath soil pipe horizontal run to stack is 15.1ft
    master bath soil pipe horizontal run to stack is 14.8ft


    1195 Master bath. WC drop is out of the picture at the right, vent connection via 3/2 Wye which has an immediate drop. soil drain pipe continues to a combo or wye (cant really tell), which connects to cut out at right; WC soil pipe has a straight run to dedicated soil stack. the WC vent is the first vent in this vent branch i.e. lav->WC->vent stack

    1196 Kids bathroom WC. WC drop is at right, soil pipe vent connection via 3/2 Wye, installed backwards, hooks into lav vent coming out of the top of the picture
    offset vertical drop through concrete wall...then turns right behind walls and connects to dry vent stack. the WC vent is the second vent in this vent branch i.e. WC->Lav->vent stack.

    1197 - Master bath vent. The plainest image I can find of the vent pipe drop as it connects to vent stack. Its about a 1 1/2 foot drop....in a vent pipe. it really is.

    Thanks in advance
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