Dismantle cast iron/lead socket joint

I want to remove a swan neck fitting from the top of a cast iron soil stack which is about 4"/100 mm diameter. This piece attaches to the vertical stack with a lead-sealed socket joint (see sketch). How can I dismantle this joint?

I don't want to damage any of the main vertical pipe, including the socket collar. I also want to avoid cutting through the swan neck if possible because everything is in the corner between 2 walls and difficult to access with cutting tools - I suppose doing this by hand with a hacksaw would be the last resort.

Am I likely to have much success by trying to twist the swan neck piece to break the lead seal? I have not tried this yet because it would involve chipping away some concrete.

Unfortunately melting out the lead seems like a bad option because of the vertical orientation and I'd probably just end up blocking the soil pipe with lead droplets.

 

If it's only lead then carefully using a hammer and old flat blade screwdriver, wood chisel or cold chisel might work. Be careful though, what you assume to be cast iron, could be asbestos.

 

You will have a fun job trying to dismantle an old lead and oakum joint.

No, if it was made correctly and the joint is still sealed then it will not twist out. Only other option is using mechanical means - drilling into the seal then using chisels etc to knock the seal out but you have the danger of cracking the bell as the cast is brittle.

Usual process would be to cut below the bell and then making a new connection.

 

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