Causes and Solutions for Copper Pinhole Leaks in Residential Plumbing Systems
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Causes and Solutions for Copper Pinhole Leaks in Residential Plumbing Systems

Research into the causes of pinhole leaks in copper piping and potential solutions.

Recently I was over at a friend’s house to pick up my child who was there for a sleepover. When I arrived they were in the middle of cleaning up after a plumbing leak in their kitchen ceiling. They said that it was another pinhole leak in their pipes, the third one so far. The house is about 20 years old, but they had only recently moved in. This caused me to look into this phenomenon further. There has been an ongoing failure of copper plumbing in distribution lines of homes on municipal water supply throughout the country, with several hotspots around Washington, D.C. and Florida. The problem has become so widespread that Maryland officials have set up a task force of government representatives and top researchers to investigate the cause and come up with a solution which they completed in December 2004. Some insurance studies have indicated that as much as $1 billion annually is spent on plumbing leaks and related damages.

The problem exists among multiple builders, copper manufacturers and installers. Once the problem is diagnosed, the system is typically removed and replaced with CPVC or PEX plumbing lines. This involves opening walls and can be very costly. Other areas with higher rates of pinhole leaks are Alaska, California, Massachusetts, Ohio, South Carolina, South Dakota, and Tennessee. Many areas in Florida have begun switching to PEX for their domestic water supplies. Along with the damage to your home and furnishings, and the cost or re-plumbing your home, there is the possibility of mold growth anytime you have a leak.

There have been several hypotheses regarding the causes of this failure, and there may in fact be several causes for the leaking depending on your specific situation. Pinholes in copper piping were first seen in well water systems with low ph, which caused an acidic reaction. This failure is now being found in homes only five years old and on municipal water. Studies have shown corrosion beginning in copper in as little as one year. There have been several theories, including water quality, material defects in the copper and electrolysis. For the most part, these have been ruled out through independent research. One of the latest theories is that it relates to the change in the anode rod in water heaters from magnesium to aluminum. Some studies have shown what appears to be corrosion consistent with aluminum oxide.

To identify the problem, the copper usually exhibits a greenish/white build-up or blemishes on the body of the pipe and you may also observe that the water has a bluish tinge. This may also be seen at solder joints, but is often caused by the soldering flux used at these points. Most leaks originate in horizontal runs of copper piping, but some are found in vertical runs.

Potential Causes

Occasionally poor workmanship is the cause when the interior of the pipe is not de-burred after it has been cut or acid-based flux is overused and not flushed out of the system. The rough interior surfaces create a micro-environment that will accelerate the corrosion. Homes and apartments that are left vacant for long periods of time have also had higher incidents of pinhole leaks.

One of the first suspected causes for pinholes was electrolysis from improperly bonded electrical systems or appliances connected to plumbing systems. It is widely understood that a small electric current can cause electrons to travel between dissimilar metals, such as copper, steel, aluminum, and zinc (galvanized piping). Much of the research and anecdotal evidence shows that where pinhole leaks are present, the electrical system is properly bonded. Lightning strikes have also been ruled out, which are prevalent in Florida, but not see to as high a degree elsewhere in the country.

Higher than normal levels of chlorine have been found to cause pinhole corrosion. When these high levels also come into contact with dissolved aluminum, the pitting intensifies and can cause even new pipe to leak within a year after installation.

Most people will not be aware of the problem until they have a pinhole leak. When viewed internally, there will be several dozen erosion pits. Unfortunately, these can only be viewed when a section of pipe is cut open and removed. A plumber that is knowledgeable with this problem should be consulted.


Some people have had success with installing carbon-based filters to remove excess chlorine. Others have switched their anode rods to magnesium to remove the source aluminum. It extreme cases when there have been several failures, you can have your piping lined with an epoxy coating or remove the copper and replace it with PEX piping.

Some research has indicated that by thoroughly flushing the system, a natural mineral patina will form on the interior wall of the piping and protect it from future pinhole leaks.

Notify your local water company to make them aware of the problem to see if there is a pattern in your area. Most municipal water suppliers send out an annual water quality report. Due to EPA regulations concerning the reduction of lead in the drinking water supply, many utilities have increased the amount of chlorine which prevents lead in existing lead-based solder from dissolving into the water in your home. As stated earlier, higher levels of chlorine can induce pitting in copper. You may also want to have your water tested by an independent laboratory to see if you have higher than normal levels of copper, chlorine, aluminum, chloramines, and Natural Organic Materials (NOM). NOM may possibly help contribute to an insoluble, stable mineral scale on pipe walls, which in turn insulates the pipe metal and fixes the mineral scale to the pipes.

This is a complicated problem, so the more you understand about the causes, the better able you will be to correct the problem before you encounter a major failure.

See my other Factoid Problems with PEX: The Class Action Lawsuits -


Washington Suburban Sanitary Commission (WSSC)

Toolbase Services

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Comments (1)

Interesting! I have exactly that problem now. Water sprays from one point. Waiting for a plumber in UK is like waiting for Christmas.