Plumbing,Re-piping,Water-heaters

WHAT IS PINHOLE LEAK?
A pinhole leak is a final breakthrough event of the progressive
attack of pitting corrosion on copper water plumbing. A copper
water plumbing system can be in a condition of having significant
damage by pitting corrosion, but not have pinhole leaks. The
challenge is how to discover pitting corrosion before pinhole leaks
develop. Discovery of such latent damage would require removal
and inspection of the internal surfaces of sample plumbing in the
system.

Pinhole leaks in copper pipes are a widespread plumbing problem
and are often expensive to identify, locate and repair. Re-piping
and other methods of preventing this leaky pipe problem can cost
homeowners and businesses thousands of dollars.

WHAT CAUSES PINHOLES IN COPPER PIPES?
Although no one knows the exact cause of pinhole leaks in every
situation, most researchers/experts attribute their occurrence to
some form of electrolytic corrosion, which is an electrochemical
phenomenon in which a metal reacts with its environment causing
it to deteriorate.

"The Washington Suburban Sanitary Commission (WSSC) experts
believe that pinhole leaks are not the result of corrosive water but
of dissimilar metals interacting and starting a battery of reactions
that just consume the pipe. Otherwise, dissolving of the copper
would be a widely spread problem.” (Washington Post, July 2000)

Copper pipe, though primarily comprised of copper particles, is not
homogeneous and contains multiple other metallic particles
including alloying metals (for strengthening the copper) and
unintentional impurities. The presence of water (an electrolyte) in
a copper pipe causes electric currents to flow naturally between
these dissimilar metal particles which, in turn, leads to corrosion.

The cell which triggers this corrosion process has three essential
components:
• anode (the metal that is corroding)
• cathode (a second metal in contact with the anode)
• electrolyte (such as water, which provides the corrosive medium)
At the anode, the corroding metal passes into the electrolyte as
positively charged ions, releasing electrons which participate in
the cathodic reaction. Hence, the corrosion current between the
anode and the cathode consists of electrons flowing within the
metal and ions flowing within the electrolyte.

The surface of one component of the pipe may act as the anode
and the surface of another component (in contact with it) may act
as the cathode. Usually, corrosion cells will be smaller and
numerous, occurring at different points on the surface of the pipe.
Anodes and cathodes may arise from differences in the constituent
phases of the metal itself, from variations in surface deposits or
coatings on the metal, or from variations in the electrolyte (water).

The ability of metals to resist corrosion is to some extent dependent
upon their position in the Galvanic Series. The "nobler" or less
reactive metals, tend to act as cathodes and remain intact, while
the more reactive metal particles act as anodes and corrode. A
more noble metal will not generate a flow of positive ions. The
reverse of this is the least noble metal, which will generate an
electrical current. The farther two metals are separated from one
another in the Galvanic Series, the more powerful is the electric
current and corrosion produced by their contact in the presence of
an electrolyte.

The illustration below shows a typical corrosion process in a copper
pipe. In the presence of water, metals in the interior of a copper
pipe (such as Copper (Cu), Aluminum (Al) and Iron (Fe)) interact
with one another which naturally causes electric currents to flow
between them. This current causes a series of electrochemical
reactions, which leads to the creation of “corrosion cells” and
ultimately to the dissolution of the materials in the pipe.

In some cases, the copper in the pipe is less noble with respect to
the surrounding metals, and acts as the anode and corrodes. In
other cases, it is more noble, acts as the cathode and the other
metals corrode. Regardless of which metal acts as the anode or
cathode, the fact is that the metals in the pipe are reacting,
creating corrosion cells and slowly destroying the integrity of the
pipe.