Why would a copper pipe in a house corrode?
Answers:
In contact with water and oxygen, copper forms an oxidized layer that actually helps protect it from further corrosion (the green patina that that the statue of liberty has is an example of that process). However problems can occur and have been well documented for decades.
Copper pipe corrosion has several different forms, A pin hole leak can cause "pitting corrosion". Another common form of corrosion in copper pipes is called "blue water" and its cause is not fully understood (The most agreed cause to-date is microbiological influenced corrosion). Check out How can I get an electric Utility line rerouted by the provider?