Nahh, been all over grounding problems causing pinholes in copper over at the electrical forum. Doesn't happen, it's corrosion caused by minerals in the water.
The contractor who built the house used I believe it was called copper "red"? it was the thinnest walled copper that could be used by code.
That's type M which can be identified by the red printing on it. Probably why some call it red copper. Type M is used for heating. Only DWV is thinner (yellow printing)but since it's for drainage you won't find it below 1-1/2". You would use type L (blue printing) for water supplies due to it's heavier wall. I'm surprised that any code allowed M for water lines.
-Hal
