Robert Laws wrote:
Thsi was discussed in 2004 but I would like to ask for further advice.

I am fitting a new WC to a 1960s vintage soil pipe. The pipe is cast
iron and joined with lead which appears to have been cast in place (not
foil wrap). I want to remove the last 'extension' piece (about 4"
long) which will leave the remaning 'female' pipe at pretty much the
exact correct height for my new WC.

The advice in the previous discussion was to dig out the lead bit by
bit and to wiggle the pipe by hand working it loose. A 1/4" wood
chisel (old) was suggested as a good tool for the job.

My question is: why is it not possible to undo this by putting a
blowtorch on the cast iron pipe that is to be removed and to heat it
until the lead melts? Is there a danger of explosion? a nager of
cracking athe iron of the bit I want to retain?

Has anyone 'dug out' lead from such a joint? Can it really be done in
a reasinable length of time? Would a plumber do it that way?

thahnks,

Robert

'In the old days whent I wer a lad' we used to use Oxy Acetlylene
torches to do this. A normal blow torch does not have enough heat to
melt the lead because the Cast Iron conducts the heat away quicker than
the blow torch applies it, i.e.it acts as a heat sink. If it is a
horizontal joint the lead just drips out. If it is a vertical joint you
have to melt the lead and the 'gaskin' below will burn and the molten
lead will drip down inside the pipe.(it never seemed to do any harm).

In your circumstances hiring a pipe cutter, cutting the pipe and using
what OP suggests, i.e. plastic adaptor seems the best bet.