I have a 2" section of ductile cast iron pipe that's in the way of a framing repair job. This pipe needs to move.

The cast iron dates to the original construction, 1938. As was customary at the time, the cast iron was joined with oakum and pure metallic lead.

In the middle is a modern retrofit that's horrible, with no actual seal between a plastic retrofit and the 1938 cast iron. This section serves a single modern sink and dishwasher. Fixing the modern plumbing is no problem. How do I cut & tie into the 1938 cast iron? I have heard that removing the lead is both hard, and will send lead chips down the sewer.

My local library offers a compression snap cutter for cast iron pipes.

2" cast iron pipe and cleanout Lovely job tying in old cast iron to a new plastic vent

  • Where is the joist going? Commented Dec 3, 2015 at 11:38
  • I don't think we have enough information, but since "the middle section has a horrible hacky plumbing job in 1.5" cheap plastic", would demoing the plumbing there solve your problem and give you the opportunity to tie it in properly?
    – alfreema
    Commented Dec 3, 2015 at 14:04
  • The plumbing in the middle is plastic and easily fixed. The question is about cutting and joining cast iron pipe. A new joist needs to slip in between the double header plate and the cast iron, to support the termite eaten floor joist.
    – Bryce
    Commented Dec 3, 2015 at 17:22
  • 1
    @personalprivacyadvocate Any house of a significant age will have obsoleted plumbing. Cast iron was superseded by ABS only ~45 years ago. My current home in Portland, OR, USA is ~100 years old in a desirable neighborhood of other 100 year old homes. It has cast iron drain pipe and steel supply lines. The steel needs replacing (it's constricted by internal rust) but the iron is still going strong... Of course, if the cast iron needs modification, it will need to be replaced with ABS.
    – bitsmack
    Commented Dec 3, 2015 at 18:40
  • I was more referring to the oakum than the iron. I think its more obsoleted than the pipe. Commented Dec 3, 2015 at 19:04

3 Answers 3


Cutting Cast Iron Pipe

The most common and quickest way to cut cast iron is the by the use of snap cutters. There are two types: scissors and ratachet.

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You can also cut cast iron with (in order of fastest to slowest) angle grinder, a reciprocating saw or a hacksaw. In order to use a grinder, you'll need room all around the pipe.

Connecting to Cast Iron Pipe

You connect to cast iron pipe by use of a rubber coupling with gear clamps. The most commonly used ones when adapting to plastic is referred to a Fernco:

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They make them in all sorts of size combinations. You just need to know the material and size that your connecting together.

Connecting to Cast Iron Hub

You can connect plastic drainage pipe to to an existing cast iron hub by use of a rubber donut insert:

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Fernco makes such a product (manufacture's site) that can be bought in hardware and plumbing stores or from Amazon.

  • Thanks. I borrowed a chain style pipe breaker from the local tool library, and despite the awkward position, the pipe snapped right off. Then I used a rubber boot (the type that goes outside the pipe). All good, thanks.
    – Bryce
    Commented Jan 21, 2016 at 18:12

I would consider cutting the whole mess out at the bottom end and connect A new “ABS” black pipe with a “no hub” it is a rubber connector with bands on each end to tighten then tie into the upper area . This will be much easier than packing oakum and poring the lead on top; everything can be fitted together prior to gluing so you know it is right where you want it then glue and know u fixed the mess.

  • 4
    It's commonly known as a Fernco coupler. If you go to a hardware or home improvement store and ask for a "no hub", they'll likely stare blankly back at you. If you ask for a "Fernco", they'll likely point you in the right direction.
    – Tester101
    Commented Dec 3, 2015 at 15:47
  • And for more clarification, Fernco is a company that makes (among other things) no hub connectors.
    – DA01
    Commented Dec 3, 2015 at 17:05
  • I also agree with the 'cut it all out'. Working with ABS is so easy that, if you have the access (which you have here) I'd just redo it all with ABS.
    – DA01
    Commented Dec 3, 2015 at 17:06
  • 1
    I am shocked to see Tester101 recommending to use a brand name rather than a proper name for once (but of course, no shock to see very helpful advice) :-) Commented Dec 3, 2015 at 17:26
  • Could you be more specific on the fittings needed to get from the 1.5 inch sink outlet, down to an appropriate model of rubber compression coupling?
    – Bryce
    Commented Dec 3, 2015 at 17:27

Given the choice of "cutting the pipe or notching a new joist" I would have to say that notching a joist would be preferable to trying to re-route a cast line. Of course re-locating most pipe can be accomplished especially with present day rubber connectors, but for the sake of expediency (if that is a concern), take the joist route. Depending on the size and location of the notch you may be required to double the joist to compensate for the cut. It may be wise to deal with the ABS/cast connection now if work space will be a problem after the joist is installed. You may be able to secure the ABS pipe with modern materials (epoxy and gap filler rods or expanding foam?), but I'm sure someone will have something else to say about that.

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