"Alasdair" wrote in message
om...
(OldScrawn) wrote in message
...
I agree with Andrew but suspect in this case the right option would be
to lose
the accessible bit of iron and replace with plastic. Probably start with
an
angle grinder. I've used the little slitting wheels on "dremel" type
tools to
slit the remains of the inner tube without threatening the socket, or
just to
put in a stress raiser so that it cracks without applying too much
force.

Thanks for that. A further question.

I don't think the cast iron pipe is 4". I appears to have an external
diameter very similar to the internal diamaeter of the 110mm plastic
pipe.


If the 110mm diameter is at the spigot on the end, then pipe is classed as
three inch. There is no way you get a 110mm (4'') pipe into it, or an
adaptor that goes the wrong way round, i.e. 4'' on top to 3'' on the bottom.
Although there are reducers that will go from 3'' above to 4'' underneath.

(see below)

Whats the best way to make the connection? Perhaps I need an adaptor
that will smoothly reduce the 110, and fit internally to the cast iron
pipe? or can I just slip the plastic pipe over the cast iron stub and
seal it up?

Also, is the cast iron likely to be a 3.5" internal diameter? Its
marked with a "C" if that is of any use!


Thanks,

Alasdair

What are you connecting to the stack ? What is already connected to the
stack ?