I disagree. It could easily have been caused by an electrolytic reaction. It might well be frozen pipes, too, but some of Tony's pipes are interior pipes, if I remember correctly.

Probably the best way to know which one is to see if there's a patina on the inside of the pipe or not. Of course, that necessitates removing the piping. But I think Tony's at the point where he has to replace the piping anyway. But if he decides to go with copper, he should definitely check that out, and possibly ground the piping better if he needs to.