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Water Pipe Leak
Metallurgical
failure analysis was requested of a corroded
residential copper water pipe following a water leak
in a private residence. Two small sections of copper
tubing, one approximately 5/8" x 4" and 0.40" wall
and the other approximately 7/8" x 8 1/2" x .52"
wall were submitted for visual examination and
metallurgical failure evaluation. Three water faucet
stream diffusers and attachment ring were also
submitted. Due to the limited extent of the
residential damage, no destructive testing,
metallographic, x-ray diffraction/spectroscopy,
chemical analysis, etc. was authorized. No water
chemistry was available.
The smaller 5/8"
diameter section was visually examined. The section
of water pipe has a small, elliptical shaped
through-the-wall hole, 0.100 x 0.120 inches, as show
below.
Photograph A:
Overall view of the smaller water pipe with the hole
denoted by a white arrow.
The larger
section of water pipe (shown below) did not contain a
through-the-wall perforation, however, the outside
surface exhibited green external
corrosion as well
as non-uniform areas of darker oxide.
Photograph B:
Overall view of larger section of water pipe with
green corrosion.
The heavily
corroded and clogged water stream diffusers/strainers are shown
below.
Photograph C:
Overall view of clogged water diffusers/strainers.
The smaller 5/8"
diameter section of water pipe was cut
longitudinally to facilitate the inspection of the
water pipe's inside surface, as shown below.
Photograph D:
Overall view of split, smaller section of water
pipe.
The inside
surface contained light to dark green friable
corrosion products. The darker green deposits were
often in the form of tubercles, which once easily
dislodged revealed a corrosion pit filled with
corrosion product. This is illustrated in the
photograph below.
Photograph E:
Inside surface of water pipe showing
corrosion/corrosion pits.
In the
photograph above, the area in the center of the tube
located just above the 3 inch marker is loosely
held. The corrosion product was lifted and turned
over then the photograph below was taken.
Photograph F
The light green
deposit within the copper area is corrosion product,
and is the result of
pitting corrosion. The pits
extend into the copper tube. Had this corrosion been
allowed to proceed, a through-the-wall perforation
of the water pipe would have resulted. A stereo
microscope (magnification 70x) view of the
through-the-wall perforation is shown below.
Photograph G:
Close-up view of through-the-wall perforation of
water pipe.
Clearly, there
is less evidence of the dark green tubercle
corrosion product on the larger section of tubing.
However, removal of the light green corrosion
product did reveal some minor putting and wall
surface attack.
Photograph H:
Overall view of limited corrosion within larger
tubing piece.
Cold water
pitting is well recognized since the research of H.S.
Campbell. It is characterized by friable (fragile)
nodule (tubercles) with underlying corrosion pits on
the waterside of copper tubing.
Metallurgical
failure analysis showed clearly that the copper
tubing wall was initially compromised by pitting
corrosion resulting from aggressive water chemistry.
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Dr.
R. Craig Jerner, Ph.D., PE specializes in accident
investigation and metallurgical failure analysis,
with over 30 years experience as a metallurgical
consultant and accident investigator. He has
testified as a metallurgical expert in over 250
depositions and more than 70 court appearances. If you or someone you know should need the services of Dr. Jerner and J.E.I. Metallurgical, please visit our web site at the buttons below, or e-mail Dr. Jerner --- 