"Andy Wade" wrote in message
...
Dave Plowman (News) wrote:

Wonder what the problem was? Chemical reaction or impurities in the
'copper'?

The following is copied from
http://www.cda.org.uk/megab2/build/pub33/33_2000.pdf

Pitting Corrosion of Copper Tubes

SNIP

I don't think any of the options described in the article fitted with the
pipe I dealt with. It carried cold water from a loft tank where oxygenation
could take effect, it wasn't down to soft water since ours is pretty hard,
and some of the pits formed at the top of the tube where carried over flux
is unlikely to deposit although some of them were at the sides and the
bottom.

I'd say free particles of a contaminant such as iron in the copper would be
a more logical cause

John