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I need to connect PVC to this old sewer pipe:

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This is the pipe that came off:

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I temporarily capped it with a 3 inch fernco and a rubber mallet. Can I permanently use a 3 inch to 2 inch fernco?

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  • It's shortcuts like a 3 inch to 2 inch fernco that led to your current malodorous encrusted disaster in the first place. – A. I. Breveleri Oct 30 '16 at 16:50
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You are looking at an attempt to attach a plain steel drain pipe to a cast iron hub-and-spigot drain pipe. The hub-and-spigot technology is obsolescent or obsolete. It was labor-intensive, quite robust, and suitable to the materials available in the nineteenth century.

You can buy hubs and spigots suitable for connecting modern materials such as PVC to existing hub-and-spigot plumbing. If you go this route you can expect to make one more labor-intensive caulked joint, and switch the rest of your pipes to modern types upstream of that joint.

You can also use a donut to connect modern plumbing to a hub. I consider this less robust but if you can fasten down the involved pipes so there is no motion at the joint it should be okay. It's a lot faster than caulking.

Here's an illustration of the hub-and-spigot method: good and bad cast-iron hub joints

Whatever method you choose, your first job is to remove the detritus of the old failed joint from the cast iron hub. Don't skimp on this -- get it all out. You'll thank yourself later.

I see that Tester101 has already illustrated a donut. Here is a picture of a PVC spigot adapter. PVC spigot adapter

With the PVC spigot you use epoxy filler (e.g. SteelStick) or hydraulic cement instead of lead.

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You need a Fernco Donut.

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It's likely that other companies manufacture these, and thet they may be known by a different name.

If you were connecting to a cut section of pipe, instead of the hub. You could use a Flexible Coupling

  • 3
    Be aware that these are designed to fit the bell of your cast pipe, and so you'll need remove the lead, oakum, or other material from it. Your first photo seems to show it all still in place. – isherwood Oct 28 '16 at 19:10
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You must drill out the lead around the reducer Ring and remove it to install the rubber gasket, and then add a reducer joint that you can glue your 3 " PVC to. I only know this because I've just done one; not too hard just takes time.

  • 1
    Welcome to Home Improvement! Thanks for the answer; keep 'em coming. You should probably take our tour so you'll know how better to contribute here. – Daniel Griscom Apr 16 at 14:26

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