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Replace Rusted DWV teed into Cast Iron

PatchogPhil | Posted in General Discussion on November 11, 2009 09:23am

Was visiting Mom, fixing a broken roof shingle. Putting away the ladder down the cellar and heard water dripping. Found the 2″ galvanized DWV is rotted/rusted through at the exposed threads at a tee. That rusted 2″ goes into the 4″ cast iron stack w/main house trap. Approx 50 year old pipes. I put a fernco-type rubber collar w/clamps on it as a temporary fix. Now the adjacent threaded connection is dripping. No pitch to the horizontal pipe, water just sits in there. I will replace all the horizontal “near” DWV piping except the 4″ cast iron.

Here is a pic. Purple arrow comes down from toilet. Blue is 2″ line from bathtub, bath sink and kitchen sink. Red goes down into main house trap. Yellow is vent that goes up from trap and out band joist.

View Image

Green arrow in above pic points to the connection I am concerned about. I will remove the 2″ rotted pipe. If the threads inside the cast iron stack are no good, what are my options to connect new drain pipe? Two-part putty at the bad threads? I do not want to use a barbed rubber insert bushing which would reduce drain to smaller than present 2 inch.

View Image

Is there enough “meat” at the 2″ hub coming out of the 4″ cast iron stack, to use a fernco socket connector (goes over the iron hub and reduces to go over PVC)??

 

Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?

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Replies

  1. User avater
    Dam_inspector | Nov 11, 2009 09:52pm | #1

    Here's what I would do. Remove the 2" pipe from the 4" stack. I think the threads in the iron will be OK. You may have to make a couple saw cuts into the 2" pipe near the top and knock out the pieces. Then thread a pvc adapter into the iron pipe. Use plenty of dope on the threads. Then you're home free to change the remaining stuff out to pvc.

    1. PatchogPhil | Nov 11, 2009 10:37pm | #3

      That is pretty much what I was planing to do.BUT.... if the threads are messed up in the cast iron stack, that is what I'm looking for suggestions. Contingency plans BEFORE I start cutting.
       

      Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?

      1. User avater
        Dam_inspector | Nov 11, 2009 11:29pm | #6

        Glue in the pvc if there are no threads.

        1. PatchogPhil | Nov 12, 2009 01:45am | #7

          Any particular glue that works on PVC to cast iron?I'm leaning towards using a two-part putty that hardens, making a water proof seal. 

          Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?

          1. User avater
            Dam_inspector | Nov 12, 2009 02:47am | #8

            Good choice. You probably want something that is rigid when cured. I also like to use permatex hardening gasket sealer.

            Edited 11/11/2009 6:48 pm ET by Dam_inspector

      2. brucet9 | Nov 12, 2009 05:54am | #9

        You can use a new 2" pipe nipple to chase rusty threads in the CI after you remove the rusted galvanized nipple. Take a hacksaw or grinder and make cuts across the threads of the new nipple at intervals so that it will act as a sort of thread cutting die to clear out the residual rust in the CI threads. Since there is no pressure on those pipes, I would think that a liberal dose of pipe dope after you clean out the threads would suffice to prevent further leakage with either galvanized or ABS nipple.If thread damage is substantial, one of the Liquid-Weld epoxy products might do the trick if you apply the stuff and then screw in the new nipple before it sets. I think an ABS nipple would be better than galvanized in that case, just in case you might ever have to take it apart again.BruceT

  2. User avater
    xxPaulCPxx | Nov 11, 2009 09:58pm | #2

    That whole section is ugly.

    I would think about removing that section of 4" where the T is and replacing it with the T that swoops down... so poopy water doesn't go into your sink drain line.

    Obviously that 2" T has to go as well.

    Tu stultus es
    Rebuilding my home in Cypress, CA
    Also a CRX fanatic!

    Look, just send me to my drawer.  This whole talking-to-you thing is like double punishment.

    1. PatchogPhil | Nov 11, 2009 10:44pm | #4

      I have considered removing that 4" CI section with the 2" side inlet. Just don't want to open up a big can of worms going upwards and especially downwards into the house main trap w/double clean outs.When replacing the 2" line I will attempt to create an angled inlet with 22.5 and/or 45 degree fittings. Mainly to create slope into the stack, and secondly to prevent poopy water splashing into the 2" drain. I know it does now - I saw the water splash out the rot holes when the toilet was flushed. 

      Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?

      1. User avater
        xxPaulCPxx | Nov 11, 2009 11:13pm | #5

        You can cut below the coupling of the bottom vertical 4" piece - this will allow you to put in a ferco and whatever new piping you need.

        With the ferncos, you don't need to worry about the old joints... let them go.

        Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!

        Look, just send me to my drawer.  This whole talking-to-you thing is like double punishment.

  3. PatchogPhil | Nov 16, 2009 09:11am | #10

    Following up..... warning, lousy cellphone pictures.

    Sawzall cut out the offending parts. Rusted nipples removed rather easily. No "digging" them out, just unthreaded with a large Stillson wrench. I was happily surprised that the threads in the stack and also the remaining 2" tee galv fitting were in good shape. Used teflon paste on the repair - no leaks.

    Here's the soil stack inlet:

    View Image

    Here's the remaining 2" galv tee:

    View Image

     

    Here's my repair, with old and new. Didn't cost much in parts, but shoe-horning the PVC between the cast iron stack and the remaining galv pipes was a struggle. I couldn't fit a PVC union in there (way too long) without removing more of the existing pipes/vent.

    View Image

    When I cut out the leaking 2" nipple(s) from the 4" CI stack, the remaining 2" line configuration moved a bit. It did not line up w/the stack 2" inlet, offset by just over an 1/8th inch. That and the afore mentioned shoe horning required trial fitting and trimming. So I used the ProFlex rubber coupler with full length metal band (NOT the corrugated type) and hose clamps. There was some "play" in the old pipes, and the ProFlex tightened up to pull them back in line.

    In hind sight I could have used all galv pipe with a galv union (much smaller than PVC union). Just replaced what was already there but add a union. Maybe I'd have had to get cut some custom length threaded pieces. Most likely a few trips back and forth.

    I also replaced the horizontal dwv and trap for the bath tub (very cruddy inside), adding more slope. And repaired two leaky copper supply fittings.

    Before and after:

    View Image

     

    "Funny" how I went there to fix a single roof shingle and found a leaky drain and 2 drippy copper supply lines. Mom wouldn't have noticed it for a month or more, she doesn't go down the basement much. Dad's birthday was Friday - he would have been 77.

     

    Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?

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