In article , Andy Wade
writes
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
---------------------------------
It should be emphasised that the number of copper
tubes affected by pitting corrosion is an extremely small
percentage of the total amount manufactured and
installed in the United Kingdom.

bit ambiguous that, does it mean that it doesn't include imported copper
tube? I understand the thin walled stuff is all manufactured overseas

The majority of copper
tubes give satisfactory service over many years. Two
forms of corrosion to which copper tubes are
susceptible under specific circumstances are recognised
and described in the literature.

A1 Carbon film
--------------
This form of pitting, sometimes referred to as €˜Type 1,
corrosion can cause premature failure in copper cold
water pipes carrying hard or moderately hard deep well
waters. Two factors are involved in this form of attack.
Firstly the water must be capable of supporting it:
organic matter found in surface derived water provides
inhibition against attack, and only deep well waters can
support it. Secondly, attack occurs only when a thin film
of carbon is formed within the bore of the tube during
the manufacturing process. The cleaning processes now
used by major manufacturers ensure that copper tubes
meet the requirements of BS EN 1057 concerning the
absence of deleterious films in the bore.

This sounds like my problem, not sure about the deep well waters though
but we're certainly hard around here

A2 Hot, soft water
------------------
This type of pitting corrosion, sometimes referred to as
€˜Type 2, is extremely rare in the United Kingdom: it
seldom causes failure in less than about ten years.
Carbon films are not a factor in this type of attack. It
occurs in hot water pipes in some soft water areas
specifically if the operating temperature is above 60oC.
This should be borne in mind when specifying higher
temperatures in an attempt to eliminate problems
associated with Legionnaires Disease. (See also section
on Commissioning and Appendix E).

A3 Flux
-------
Excessive use of flux resulting in flux runs within the
bore of the tube may cause corrosion and should be
avoided. Hence the need to use fluxes sparingly and
according to manufacturers instructions.
/copy


--
David