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Thread: PVC into Cast Iron with standing water

  1. #1

    Default PVC into Cast Iron with standing water

    I know there are lots of PVC into cast iron discussion, but I have a problem I haven't seen answered. I live in a condo building built in 1840. We recently bought our condo and remodeled the bathroom. The sink, tub and toilet all join into one big PVC pipe before connecting to the cast iron building drain with a rubber no hub fitting.

    Everything worked great, until the main drain plugged up and water backed up while showering. This left a lot of water in the PVC pipe above the no hub connection and the pressure pushed through the fitting, destroying a ceiling of my downstairs neighbor.

    I agree the clog is in the building pipng, not my plumber's work. The plumber says the fitting simply was not designed to handle the pressure from water not flowing through. I also have found out this drain clogging problem has showed up intermittently over the years and I don't expect to convince the condo association to rip out the walls and replace the pipes without a LOT of discussion (e.g. Not any time soon).

    We've snaked the drain and cleared the block, but the pipes are in rough shape and I expect this to come back. My question - Is there a connection the plumber could use for the PVC to cast iron connection instead of the no hub rubber fitting that would be able to hold the standing water above it without leaking? I need warning the drain is backing up before water starts coming through my very nice neighbor's ceiling.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    The fitting should be a neoprene sleeve with a metal reinforced sleeve over it. If it is just a rubber sleeve with a hose clamp at each end, it is not the proper one - the reinforcement is required to keep the pipes aligned. The other type is okay for underground where you backfill around the pipe to keep it aligned, not on an in-line freestanding pipe.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default connection

    Any "proper" connection will hold considerable back pressure, and definitely more that could build up in your drain system without overflowing out of the toilet, sink, shower, or tub.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    If it is just the rubber sleeve with the clamps at the end, the pipes are likely not in-line, a catching point for toilet paper, etc and the source of a clog.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5

    Default

    Thanks for your responses, guys. Very helpful.

    With some more investigation - The no hub fitting is heavy duty with a steel band. They've put a new one on and tested with the water backed up again and it holds. Both the new pipe and the old were not strapped properly. The old pipe was not quite pitched properly. It seems the weight of the water caused sagging at the no hub fitting, making a "V" shape, and probably the cause of its failure. Both old and new pipe are now strapped properly to maintain pitch and the fitting seems to hold the pressure no problem.

    Based on the amount of time it took running the water before the backup reached that point, we're guessing the clog is further down the drain. We're going to get it professionally cleared and test again.

    Thanks for the advice and let me know if you have other thoughts.

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