There are two options to properly tie into cast iron plumbing. One, using a no-hub coupling, attaches a straight section of cast iron to a straight section of PVC. The other, a hub o-ring, lets you insert a straight section of PVC into the hub of cast iron. Your particular situation will determine which one you choose.
No-hub:
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-Rubber coupling with a metal band around the outside and 2-4 clamps
-The metal band prevents sideways shearing forces from seperating the joint
-DO NOT use a Fernco coupling, they do not have a metal band around the outside and are meant for under ground use
-The 4 clamp couplings are of better quality, they can be found online and at plumbing supply stores.
1. Make a smooth cut on a straight section of cast iron with a chain cutter. A sawsall can also be used but it will take several blades and a lot of time.
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2. Loosen up the clams, remove the band, and slide it onto the pipe
3. Slide the rubber coupling on the pipe. If you are building from that point (running plumbing starting from that point) insert the PVC. If you are attaching an already built section to that point (you only have a little wiggle room in the new plumbing, enough to swing the PVC back and forth a little) roll the rubber coupling back onto itself on the cast iron, swing the PVC into place, the roll the coupling back into the proper position and onto the PVC.
4. Slide the metal sleeve over the coupling and tighten the clamps
Hub o-ring:
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-Rubber o-ring that takes the place of the old lead/oakum joint
-Using an existing hub on the cast iron pipe, you can insert a PVC pipe and have it be leak-free
1. Remove the cast iron above/beyond the hub connection you will be using. Break/cut it back to as close to the hub as you can get, a chain cutter or a hammer both work. Be very careful that you do not break or crack the hub in the process.
2. Find a drill bit that is slightly smaller then the lead/oakum joint and turn it into swiss cheese. Drill down the depth of the joint and drill as many holes as possible. Once it is properly drilled you can then pry out the lead and oakum.
3. Remove the cast iron pipe from the hub and clean up the inside hub surface. A small wire wheel and a drill work well.
4. Insert the rubber o-ring into the hub.
5. Lube the inside of the o-ring and the end of the PVC with some Dawn dish soap or similar. Insert the PVC into the o-ring the best you can and then pound it into the o-ring. I use a piece of scrap wood over the end of the PVC and a 5lb sledge hammer.
