On 13/11/2014 23:51, Ian Jackson wrote:
In message , Lobster
writes
Investigating the cause of a damp patch on an internal wall, I
discovered a
crack in a cast-iron downpipe; looking at it more closely I found that
the
crack actually runs the entire circumference of the pipe, and it's
possible
to raise the upper section and see daylight between it andthe lower
section.

********.

I know it would be a relatively trivial matter to replace the downpipe
with
a 'nice new' plastic item; however, I'm rather attached to my original
100-
year-old cast-iron rainwater goods, and I'd really prefer to hang on
to it
and repair it instead.

What would be the panel's reccommended method?

Thanks

I'd be tempted to fashion a sleeve - possibly from a bit of plastic pipe
of similar diameter or slightly larger diameter. Cut the plastic pipe in
half - into two 'shells' - that can be offered up to each side of the
cast iron pipe. To get a good fit, a hot air gun can be used to soften
and slightly re-shape the plastic pipe.

The actual gap in between the two halves of the pipe could be bridged by
self-amalgamating tape (although this might not be necessary)

Butter-up the inner sides of the two halves of the shells with car body
filler (preferably the plastic type of Plastic Padding), and place on
each side of the cast iron pipe to form the sleeve. Hold in place with
wire or very large cable ties - or something much more businesslike -
like say several large Jubilee clips ('in series', as required).

I'd go for an *internal* sleeve; standard downpipe is probably too
large, but cut a suitable width axial slit so that it springs inside.
Fix with non-setting mastic, this can also be trowelled into the
external crack. Obviously, you would need to take down at least part of
the downpipe to do this.