3.5" cast iron pipe to pvc

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by karch03, Jul 10, 2012.

  1. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    Hello,

    I located a toilet flange in my basement this past week and I am wanting to install a half bath now. My issue is that the waste stack sits really close to the flange. It seems like I will need to angle it the opposite way with PVC and mission couplings, add a cleanout and then angle it back in. If I measure the current stack from left to right I am getting a measurement of 3.5". After searching this issue online I do see it comes up but there is no real clear solution to reduce the pipe to 3" pvc or increase it to 4" pvc. Any ideas? setback.jpg closeup.jpg
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    Drain pipe is by inside dimensions, so that's probably a 3" drain line. Except with say a 4x3 toilet fitting, you can't go from a larger to a smaller drain line.

    Do you need to move the existing toilet flange?
  3. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    idea3.jpg Jadnashua,

    Moving the flange would be a possibility. However, I was hoping to "T" off the replacement PVC stack for a sink as well. Something like what I attached. I guess I could move the flange and leave the cleanout and then just do a clean straight "T" in with PVC to the stack? Thoughts?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,242
    Location:
    Cave Creek, Arizona
    On the surface, it appears that the existing flange is improperly installed and you cannot just "put a tee" in the pipe for a sink. From the hub direction, it appears that the flange is connected directly to a "T" of some kine with the pipe buried IN the concrete, not beneath it, which should be impossible to do and do it correctly. BOTH the toilet and sink need vents which they do not have now. You also do NOT have vertical room to make the offset the way you drew it.
    Last edited: Jul 11, 2012
  5. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    HJ,

    Looks like I am stuck! Kentucky code doesn't allow for wet venting so vents would need to be installed. Guess I will be calling a plumber.

    Thanks!

    Last edited by a moderator: Jul 11, 2012
  6. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    I got a union pipe fitter telling about a cheater valve thats "technically" legal in KY. Any chance I can just "T" the pipe for a sink drain and add the cheater vent? I can probably put a extender flange on...float the floor with leveler concrete and leave the cleanout where it is. Thoughts?
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    That 'cheater' valve is technically an AAV (air-admittance valve). They are a one-way (air in) valve, don't always work since sometimes air needs to get out, they can't be burried in the wall so they must have an access panel since they do fail. Most inspectors will only approve their use IF there's no other way, or at least no easy way. You should avoid it, and it may not work well with a toilet and a sink.
  8. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    Jadnashua,

    I'm not truly concerned about the venting of the toilet. The flange is cast iron which leads me to believe its been there since the house was built in 1939. My guess is if it worked then it should work now. Right? If I can use the AAV on the sink then I should be golden. Any issue with cutting the stack and doing a straight up and down "T" for the sink drain with proper couplings? Thanks!
  9. Terry

    Terry Administrator Staff Member

    Messages:
    15,413
    Location:
    Bothell, Washington
    If there is a toilet on the stack in the picture above, and someone flushes it, it can move the water in the bowl below. If it hasn't done this yet, it will if you ever change to a better toilet with a 3" flush valve.

    Your best bet at this point, is to break or cut concrete, plumb the lower toilet correctly, move the cleanout and provide for the sink.
    The toilet downstairs needs the vent, as does the sink.

    With little space, it's sometimes easier to place a cleanout above the tee for the sink.
    If you break out a little concrete there, you can lose all of those poured joint fittings quite easily.
  10. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,395
    Location:
    Yakima WA
    Half ass jobs are just that. They almost always come back to haunt you. Can't fault you for looking for an easy way to do the job, but that just isn't always possible. Breaking out concrete really isn't that hard. You can rent a small rotary hammer/drill that will do the job. Get the area exposed yourself, then pay the plumber to do the technical work.
  11. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    You are correct....I should apply the 7 P method (proper prior planning prevents piss poor performance). So....my best option is to expose the flange, remove the waste stack from cleanout to flange, rework the flange coupling to CI and add a sink down pipe (no need for "T"), tie both to a vent and take it to the roof, then add a cleanout to the waste stack with a coupling?
    Last edited: Jul 11, 2012
  12. Terry

    Terry Administrator Staff Member

    Messages:
    15,413
    Location:
    Bothell, Washington
    I hadn't seen that before. I like it!

    It sounds like you are on track.
  13. karch03

    karch03 New Member

    Messages:
    7
    Location:
    Kentucky
    Thanks to all on this forum! You guys truly are a wealth of knowledge! As a home owner I am sure I will be back to pick your brains again. Thanks again for the help!!!
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