This is a common problem. It is being investigated all over the country.
IF the hole is wider on the inside of the pipe, it is caused by a change in the water treatment. Many water companies are using a new chlorination system that is suspected of causing this problem.
IF the hole is wider on the outside of the pipe, it is caused by soil side corrosion. This can be caused by the use of some hair driers in the home that use diodes to control the speed of the fan. The diodes create pulsating DC which will corrode copper or steel pipe. This may have even happened in concrete incased copper pipes.
I have seen entire neighborhoods of copper water service lines destroyed by a miss-wired cathodic protection system for a natural gas distribution system. The anode lead was inadvertently connected to the power neutral. Thus each home's neutral-to-water pipe bond caused the water pipe to corrode.
Some other sources of information:
http://www.wssc.dst.md.us/copperpipe/copperpipewp.cfm
http://www.epa.gov/nrmrl/wswrd/cr/pubs/wqtc.pdf
http://www.epa.gov/nrmrl/wswrd/cr/pubs/awwa2005.pdf
http://www.corrosionsource.com/discuss2/ubb/Forum49/HTML/000012.html
Just in case the link is deleted the text follows:
After years of research, Dr. Marc Edwards, professor of Civil and Environmental Engineering at Virginia Tech has proven that the recent epidemic of pinhole & slab leaks in copper pipes is caused by the water.
In order to comply with the Safe Water Drinking Act of 1991, water treatment plants began disinfecting our drinking water with Chloromines instead of Chlorine. This removed the Natural Organic Matter (NOM) from the water which did make our water safer to drink, but in turn made it very aggressive to the copper pipes.
With NOM in the water, the copper was able to develop a protective film coating. Like when you put a penny in water, it would eventually form a blue-green patina. As the protective film develops it protects the pipe from the water and the corrosion rate decreases. However, the changes made to our water chemistry have interfered with the formation process resulting in accelerated pitting and corrosion.
ref: http://www.nace.org/mponline/2004/0405018.pdf
Tom Gibb
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