Water below 7.2 is acidic. I don't know if water with your PH would eat copper as fast as you have described though. I don't think electrolysis could be the culprit either but stranger things have happened.
I would ask the electric company if they have any experience with this problem.
A few years ago, I found out that my well had a broken coupling at 40 feet. It took years, but the surface water with a PH of 5.5 found it's way down to that coupling and was turning my shower blue. I now have a new well and that one is plugged with bentonite. That's about the extent of my experience with low PH and copper.