Copper is used to make products such as coins, electrical wiring, and water pipes for household plumbing. The primary sources of copper in drinking water are corroding pipes and brass components of household piping systems. Drinking water may have elevated levels of copper include a metallic taste or blue to blue-green stains around sinks and plumbing fixtures.

The corrosion leads to the release of copper ions and the deposit of corrosion byproducts on the pipe wall. The solubility of these byproducts ultimately determines the level of copper at our taps. The only way to accurately determine the level of copper in drinking water is to have the water tested by a state-certified laboratory.

There are two types of copper corrosion

• Uniform, and
• Nonuniform

• Low pH
• High alkalinity, and
• The presence of sulfates or nitrates

Uniform corrosion is identified by the presence of a relatively uniform deposition of copper corrosion byproducts across the inner surface of a pipe wall.

Nonuniform corrosion is the isolated development of corrosion cells across the inner surface of a pipe wall.

Pitting corrosion can lead to “pinhole” leaks in the pipe, which could result in water damage and mold growth. Pitting corrosion is most likely to culminate in pinhole leaks in copper plumbing. It is the non-uniform localized attack of the wall of copper tube, pipe, or fittings initiated on the interior/waterside surface in the domestic water distribution system, in which only small areas of the metal surface are attacked, while the remainder is largely unaffected. Pitting corrosion starts on metal surfaces for unknown reasons, and some combinations of water chemistry factors allow the process to continue while some do not.

Pitting corrosion can be classified into three types:

• Pitting is associated with hard or moderately hard waters with a pH between 7 and 7.8, and it is most likely to occur in cold water. The pitting is deep and narrow, and results in pipe failure.
• Pitting occurs only in certain soft waters, with a pH below 7.2 and occurs rarely in temperatures below 140° F. The pitting that occurs is narrower than in the upper type, but still results in pipe failure.
• Pitting occurs in cold soft waters having a pH above 8.0. It is a more generalized form of pitting, which tends to be wide and shallow and results in blue water, byproduct releases, or pipe blockage.

Several studies and research projects have been conducted to determine the possible cause of pinhole leaks in copper pipes, but no definitive causes have been established.