I'm experiencing a problem w/our copper waterlines/pipes corroding from the inside out. I purchased this home back in April 2006. So far the corrosion appears to be limited to just the Hot Water lines, but I'm afraid to take a look inside the cold water lines.
What's happening is we keep getting pinhole leaks springing up throughout the hot water lines, and when I recently repaired two holes/leaks I looked at the inside of the lines and saw a lot of corrosion which I have never seen or experienced before. I had a home inspection completed by a professional before I bought and closed on the house, and they even identified a leak that the previous owner had to fix prior to the closing. Is there anything else I can do other than replace the entire waterline system? Also, is there anything I can do because I feel this was an existing problem that the previous owner knew about?
Thank you in advance for any advice you can provide and for helping so many through your show!
askatman 12/10/06 7:19pm.
Copper has been used for domestic water piping for over 50 years. Copper pinholes are a condition that is somewhat newer. Pinhole leaks form on the inside of copper piping and erode the wall of copper resulting in holes that leak. Opinions vary of the cause but many experts believe the corrosion due to a chemical reaction between the water and the copper.
ToolBase Services,  the housing industry's resource for technical information on building products, materials, new technologies, has found that pitting corrosion can be classified into three types:
** Type I 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.
** Type II 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 Type I, but still results in pipe failure.
** Type III 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.
To read the complete Toolbase Case Study on pinhole leaks, click here. 
Repairing pinhole leaks is done by applying external solder to the holes, by replacing small sections of pipe or in the worst case scenario, by re-plumbing the entire home.
If your problem is severe, I'd recommend you approach this in much the same way as you would if you were suffering from rusted steel plumbing common in homes built from the 1920's on.
1. Repair as needed as leaks they develop.
2. Plan and budget for a more major upgrade of the accessible parts of the plumbing system in the near future. By accessible, I mean those that are visible and accessible from a crawlspace or basement.
3. Replace all the inaccessible pipes only if leaks develop. That being said, if you ever have need to open a wall or ceiling and find copper pipes, never replace the drywall without first replacing the pipes.
As for what you should replace the plumbing with, I'd recommend PEX. PEX is cross-linked Polyethylene and a relatively new type of plumbing pipe that is showing great promise due to it's ease of installation, lower cost and energy saving benefits. To learn more, visit the Plastic Pipe and Fittings Association (PPFA) website for PEX information. 
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