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Thread: Fixing a PVC to cast iron connection

  1. #1
    DIY Junior Member Auream's Avatar
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    Default Fixing a PVC to cast iron connection

    I am re-doing a bathroom and I've been lurking on here for a while. Finally have a question that couldn't be answered by searching. I'm going to be tiling and changing the height of the floor, so I needed to cut off my toilet flange and install a new one a little bit higher (this will also let me leave off the flange while I add underlayment and tile making everything much easier).

    Anyway, I cut out some of the subfloor (which was showing dry-rot anyway) and noticed that at some point the last foot or so of cast iron waste pipe going up to the toilet had been replaced with PVC. It appears that whoever did it pushed the PVC pipe into the spigot of the cast iron, and packed it with oakum, and that's it. No sign of lead or anything to actually hold the oakum in, unless I'm missing something. No idea how long its been like this, but this isn't sufficient, is it? In addition, this section of PVC pipe is slightly loose, which I noticed when I accidentally pushed on the flange and the pipe twisted slightly in the socket (not sure if its a problem or to be expected). On top of that, this section of pipe appears (maybe its just an illusion) to slope the wrong way (looks like its maybe 1/8 inch lower by the toilet flange than where it goes into the cast iron).

    I wanted to take a pic or two but I sat on my camera yesterday and broke it while taking pictures of the renovation

    Anyway, my thinking is that I might have two options:

    1) Try to fix what's there by packing in lead or some acceptable substitute, and seeing if I can get the PVC to slope the right way.

    2) Pull out all the oakum and PVC, clean out the spigot, and use a rubber donut (Ty-seal?) to attach new PVC.

    Any suggestions on which of these options is the way to go, or is there a better way? Thanks a lot!

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    DIY Junior Member Auream's Avatar
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    On further inspection, it looks like the slope might be okay... end near the toilet flange looks like its maybe 1/8" higher than near the cast iron, separated by about 8 inches. I was doing some searching and came up with something about using a lead wool to pack in the oakum instead of molten lead. Is it possible that is what I'm seeing in the joint and not the actual oakum? There's basically little black fibers that are kind of sticky packed into the joint, I assumed it was the oakum but would lead wool look at all like that? Crossing my fingers that this is okay and I can just leave it and get on with my already too long project

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    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    There is a product called lead wool that can be packed on top of the oakum.

    John

    http://www.terrylove.com/lead_joint.htm

    Last edited by Terry; 06-04-2010 at 03:39 PM.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by johnjh2o1 View Post
    There is a product called lead wool that can be packed on top of the oakum.
    Or, just today I found some Harvey's "Soil Seal" that can be used on top of oakum ... but the place where I got it does not stock oakum!

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    DIY Junior Member Auream's Avatar
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    Anyone know if HD or big blue stock this "Soil Seal" stuff or do I have to check out a plumbing supply house?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    I think you'd be better off using a rubber donut in the hub. These are approved for the transition from CI to PVC or ABS plastic pipe. No oakum, or lead, just a compression fit. They generally are stocked in two sizes, normal and heavy duty based on the type of cast iron pipe you have. But, since those sizes aren't exact, and the donut has to be sized correctly for the pipe to seal properly, you may have to order one. They come in some fractional increments in size for various sized hubs. Check out www.fernco.com.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by Auream View Post
    Anyone know if HD or big blue stock this "Soil Seal" stuff or do I have to check out a plumbing supply house?
    I got mine at Ace Hardware, but the rubber donut Jim mentioned would be simplest if you can separate the fittings enough to get one in. My own situation has a 2" CI line draining into a 4" PVC pipe, and it will be best if I can use a pipe-to-pipe rubber coupling since the connection is horizontal and exposed to roots.

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    DIY Junior Member Auream's Avatar
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    Quote Originally Posted by jadnashua View Post
    I think you'd be better off using a rubber donut in the hub. These are approved for the transition from CI to PVC or ABS plastic pipe. No oakum, or lead, just a compression fit.
    I agree thats probably the BEST way, but at this point in my already-taking-way-too-long bathroom remodel I'd settle for a code-acceptable way rather than the best way The PVC is already stuck into the cast iron with oakum, which I'd have to remove and clean out very thoroughly if I wanted to use a donut. Adding some soil seal over the old oakum sounds like a much easier solution. Apparently the oakum without any lead or sealing has been holding for at least since I've owned the house (no signs of leaks), but I realize its wrong so I'd like to fix it without spending too much more time and money.

    Thanks! I'll check out Ace hardware for the soil seal, there's one walking distance from my house.

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