Copper Pipe Deteriation

Copper pipe has been in use for domestic plumbing for more than seventy years. Only recently have problems begun to develop. Research has been done but no definitive answers have been developed. Speculation includes soil characteristics, water quality, and even the flux used to solder the joints. Because most of the cases have occurred with pipe buried in the ground (in areas where slab-on-grade construction is common), the most likely cause is something to do with soil and a chemical reaction related to it.

A recent article in the Journal of Light Construction (December 1999) noted a number of possible causes, including the following:

• Corrosive soil
• Acidic water
• Aggressive flux
• Sloppy installation

One builder in California has encountered numerous problems that led to repair costs of several hundred thousand dollars in more than sixty new homes.

The city of Jacksonville, Florida has encountered such widespread problems that it has taken the somewhat extraordinary step of banning copper piping in residential construction.

Some builders in the Southwest (notably in the Phoenix area) are encasing their underground pipe in insulation to help isolate it from the soil. Others are simply not using copper (where plastic is permitted by local plumbing codes) in certain soil types.

Most problems seem to be occurring in new homes, generally those less than ten years old. According to one researcher at Virginia Tech, "In the soil environment, the number of possible causes of corrosion are infinite: galvanic, microbial, conductivity, alkalinity, phosphorus, or organic."

What is interesting about this situation is that the exact cause continues to be a mystery although the problem has been known to exist for the last five to ten years.

In some cases where the pipe is visible and exposed, green spots develop that eventually turn into pinholes and slowly dripping leaks. Clearly, in these situations, the problem is not the result of exposure to unusual or aggressive types of soil.

From those researching the problem, one recommendation that has emerged is to thoroughly flush the pipes after new construction and to be sure the pipes do not remain unused and dry for more than a brief period of time after the plumbing work is completed. Such action would generally eliminate the risk of flux or other installation- related contamination.

I have encountered very few cases of copper pipe deterioration. However, until the mystery is solved, be aware that deterioration in copper piping is a problem, and its exact cause remains unknown.