Peter wrote:

I am about to connect 4 inch waste from a new attic conversion to an
external cast iron one. Currently it rises to above roof level. Some
questions:-

As my angle grinder wont cut thro 4 inches should I cut twice ie make a sort
of inspection hole and hacksaw the back or is there an easier way. (for
direct connection at attic floor level)
Should I replace all to ground level or to existing 1st floor connections.
Will new plastic fit inside old cast iron joints.

A hacksaw will not cut cast iron without wearing out both yourself and
the blade quickly.
Angle grinder with cutter blade around the outside. There will be a 3
inch or so section that you cannot reach toward the wall, once you
cannot cut any mpre, just whack it with a hammer, it'll snap reasonably
claenly between the 2 ends of the cuts.
If mine, I'd replace all above the cut with plastic. Numerous adaptors
can be bought to mate them up.
Alan.

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