Pinprick hole in copper pipe
 

About 6 months ago we had our lead rising main replaced with
copper. Yesterday it developed a small leak from mid-way along
a section of pipe. On cutting it out I found the pipe showed
no signs of having been abraded on the outside; instead there
was a pinprick-sized hole, and inside the pipe there was a
small (3mm) cluster of green stuff (presumably, copper oxide).

I have never encountered this before. Would it be due to a
flaw in the pipe, or is there something (e.g. some other
metal) which can lodge on the inside of a pipe and rot it?

On 13 Jun 2005 00:40:06 -0700, wrote:

instead there was a pinprick-sized

Pinholes are often caused by uncleaned flux residues. Any sign of that
on the outside?

and inside the pipe there was a
small (3mm) cluster of green stuff (presumably, copper oxide).

Copper oxide is either red or black, for cuprous or cupric oxides (I
forget which is which). However most other copper salts are blue or
green, so it could be almost anything.

I have never encountered this before.

Nor I.

Would it be due to a flaw in the pipe,

It would be a rare flaw that left a pinhole in copper pipe - they do
happen, but they normally cause splits. It _might_ be an inclusion, that
then gave rise to corrosion.

or is there something (e.g. some other
metal) which can lodge on the inside of a pipe and rot it?

This could certainly happen, but I'd be surprised that such a
contaminant could sit there without getting washed out.

Any chance that the hole came first, then the crystals formed around it?

In article .com,
wrote:
About 6 months ago we had our lead rising main replaced with
copper. Yesterday it developed a small leak from mid-way along
a section of pipe. On cutting it out I found the pipe showed
no signs of having been abraded on the outside; instead there
was a pinprick-sized hole, and inside the pipe there was a
small (3mm) cluster of green stuff (presumably, copper oxide).

I have never encountered this before. Would it be due to a
flaw in the pipe, or is there something (e.g. some other
metal) which can lodge on the inside of a pipe and rot it?

I once had a similar hole in a Wicks end feed elbow. But IIRC these are
cast, rather than drawn as tube tends to be.

I'd guess at an impurity in the copper alloy.

--
*Young at heart -- slightly older in other places

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Andy Dingley writes:
On 13 Jun 2005 00:40:06 -0700, wrote:
Would it be due to a flaw in the pipe,

It would be a rare flaw that left a pinhole in copper pipe - they do
happen, but they normally cause splits. It _might_ be an inclusion, that
then gave rise to corrosion.

ISTR a batch of very low quality copper pipes around the early 1970's
with this problem, due to contamination with iron or carbon or something.
Service live turned out to be about 10 years before they were leaking
all over the place.

--
Andrew Gabriel

Andy Dingley wrote:
Pinholes are often caused by uncleaned flux residues. Any sign of that
on the outside?

No... and this was a few feet from the nearest soldered joint
on that pipe, though there was one on another pipe nearby.

Any chance that the hole came first, then the crystals formed around it?

Could be. Do you think anyone (plumbers' training college?)
would like a look at it? If not, I might just send it to my
local university materials science department on spec.

wrote in message
oups.com...
Andy Dingley wrote:
Pinholes are often caused by uncleaned flux residues. Any sign of that
on the outside?

No... and this was a few feet from the nearest soldered joint
on that pipe, though there was one on another pipe nearby.

Any chance that the hole came first, then the crystals formed around it?

Could be. Do you think anyone (plumbers' training college?)
would like a look at it? If not, I might just send it to my
local university materials science department on spec.

I thought there was a whole batch of duff copper pipe from a couple of years
ago that is now springing pin-hole leaks. Due to carbon granules in the
copper I think.

I think also the supplier/manufacturer is/was providing compensation, as I
am sure when my brother was in the plumbing trade a lot of his work was
existing pipe replacement, all paid for by the pipe manufacturer.