Pinhole leaks common in copper water pipes

Q. In the past year I've had three pinhole leaks in my copper water pipes. My insurance company has refused to pay any more claims for damage caused by leaks, and the cost to repipe my house is more than I can afford. When I asked my plumber why these leaks keep happening, he didn't have a definite answer. I thought copper piping was supposed to be good quality. Why do these leaks keep happening?

A. As copper plumbing becomes old, pinhole leaks become increasingly common. The primary cause for this, however, is not merely aging of the pipes, as we shall see. Unfortunately, pinhole leaks in copper pipes typically occur in places where they are not observed until there has been significant water damage and mold infection. Plumbers have varying explanations for these leaks, but several causes are widely recognized within the industry. The three most common of these are chloramines in municipal water systems, particles of corrosion from aging water heaters, and high water pressure inside the pipes.

Chloramines are used to disinfect bacterial contaminants in our drinking water. They have become a substitute for chlorine in order to comply with EPA standards established in the 1990s. Unfortunately, chloramines are a major cause of corrosion on the interior surfaces of copper pipes, resulting in pinhole leaks and water damage in homes. In communities where chloramines have been added to the water, leaks have become a costly nuisance for property owners.

Pinhole leaks can also be caused by particles of corrosion from old water heaters. When the interior of a hot water tank begins to corrode, steel particles can accumulate inside the copper hot-water pipes. When dissimilar metals (i.e. copper and steel) are in contact in an aqueous solution (water), electrolysis occurs, causing the interior surfaces of the copper pipes to deteriorate and eventually leak. One way to prevent this from occurring is to change the anode in your water heater approximately every five years. This can also prolong the life of the water heater.

Lastly, in homes where there is high water pressure, water flow in the pipes occurs with increased force and velocity. This can cause increased erosion of the interior surfaces of the pipes, especially at elbows and tees, where the direction of flow changes inside the pipes. Pressure regulators are recommended for all homes that have high water pressure. 80 pounds of pressure is the maximum allowed by the plumbing code, but 60 pounds is the maximum recommended pressure.

A long-held misconception about copper plumbing is that it is intended to be permanent. When copper water piping became the standard of the industry in the 1960s, it was actually expected to last for 25 to 40 years. Therefore, failure of copper pipes in the early 21st century should surprise no one.

In new residential construction, PEX pipe (a type of polyethylene) has replaced copper as the industry standard because it is easier to install and is regarded as unlikely to deteriorate. However, one of the little-known aspects of PEX is that rodents like to chew on it (another source of pinhole leaks). For some interesting facts about this, do a Google search for "PEX and mice."

• To write to Barry Stone, visit him on the web at, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

© 2014, Action Coast Publishing

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