In article 2012070413331143447-info@coukinvalid, James
writes
On 2012-07-03 21:35:07 +0000, fred said:

Agree it is likely cast iron, I have seen one with a similar collar
from a 60's build, the collar was sealed using lead wool compacted with
an offset compacter/chisel type tool.

I'm still not sure. Other than a magnet, is there a test?

I'd cut it off 2" or so from the wall to get a lower entry and use a
flexible pan connector to mate with the inside of the pipe. They're
meant to be self sealing but I'd add sanitary silicone to the
compressible vanes to make sure.

That's pretty much what I had in mind. How far down the pipe would you
aim to get the flexible connector? Does further = better? I suppose
there's a danger it won't seal properly if it's halfway round a bend
instead of in a straight section.

It wont bend until it is through the wall so you have at least 4"
straight there so nowt to worry about.

You want the pan connector to go into the pipe until it bottoms out or
until all the fins are in which could be 2-4" depending on type.

From your other pics it's def a cast iron stack, that straight vent
section at the top may be something lighter.

Other comments about the pipe being brittle and cracking are valid hence
my suggestion to cut it 2" from the wall so that you can have another go
if it breaks. Maybe start further away then re-cut closer once you have
more confidence also noting that the further from the wall the higher
the pipe will be and that it will need to match your new pan. My choice
could be a 110mm angle grinder with cutting disk, mark your cut line,
score round first a mm or 2 with the grinder then go progressively
deeper until it is cut.

Chose the right distance and you can use a straight pan connector, which
is better than flex. Smart move would be to get a few likely bits in
from a place like BES, they're not expensive and it means you have
exactly the right bit to hand no matter what.

See the bottom of this page:

http://www.bes.ltd.uk/products/121.asp

Distance from the wall will be set by your pan/cistern combo, close
coupled?

Re comments about breaking into cast iron joints/stacks, just don't go
there unless you have to, there is a high risk of breaking the collar if
you do as it is all so brittle. When you do have to do it, you smash the
ingoing pipe with a hammer, stuff newspaper in the hole to catch the
bits then have to chisel out the stub of the pipe form the socket so not
unsurprising that it often ends in tears.

No need to disturb a cast iron stack in good condition, it should last
a century. Hopefully the building is not 99yrs old ;-).

Probably about 120! But I suspect the first bathroom was installed in
the 1930s...

Thanks for the advice.

You're welcome and good luck!
--
fred
it's a ba-na-na . . . .