pinhole leaks

A while back I reported a pinhole leak in my whole-house RO system. I have now installed a separate RO system in each bathroom, thus eliminating the need for the 1/2" poly tube running through the attic. I now have the section with the pinhole leak on the bench but cannot see the pinhole...

I'm looking for and would appreciate some someone independent advice on this issue because every plumber and water quality expert gives me a different answer. Setup: 1994 Construction, Large home with many feet of copper pipes and an guest house that is quite far away. Current: Water Storage...