The very first issue, that should of been addressed already, is to stop guessing if there is a water issue. I lived in a neighborhood where this exact scenario developed. The issue was that the water was too acidic, and it was discovered, a decade later, when the pinhole leaks first surfaced. The solution was to install water treatment that neutralized the acidity. f you have water that will eat metals, IMHO, it's needs to be corrected, and patching or replacing piping is only addressing symptoms, not the cause. Remember, once you change all the lines to PEX and carefully eliminate as much metal from the system, the water is still free to attack the remaining brass and copper in things like shower valves and kitchen faucets.
The next issue is that the water treatment industry is a culture of thieves and scumbags. The very last thing I would do would be to call a high pressure treatment company, who will charge you thousands, then hundred a year to maintain the system. First, get the water tested at a real water quality lab. They will give you a sample bottle and instructions for how to draw a sample. Then start learning online exactly how to address the problem, and what equipment you need. Even if you have to order everything online, and pay a plumber by the hour to install it, you could end up saving thousands over what your local big name treatment company charges.
I started building homes a few years ago, in a region with a soluble iron problem in the water. The "only" solution the locals knew of was a local water treatment outfit the could cure it. I went to their showroom to see the system. The saleswoman accidentally called one part of the system the "brine" tank. This was enough of a clue that I used that, and a model number on another piece of the system, to determine that it was nothing but a cleverly relabeled water softener system. Like many in the industry, she was such a damn snake that she flat out lied, and claimed that it was NOT a water softener, when she contacted me later. They wanted $3000, for the system, installed. I did my first one with a name brand water softener unit for one of the big box home improvement stores. It was less than $400 for all the parts, and east to install. Problem solved, $2600 stayed in my pocket.
One last point. The thin copper claim may be valid. That said, it's often assumed to be the problem, but typically the first pin holes show in the elbows. Most elbows are "drawn". This means that they are pieces of tubing that are stretched in the shape of an elbow. Pulling the material causes it to thin out, and many of the leaks I have repaired are just about dead center of the elbow. Hopefully, if you have access to any leak, you are using Shark Bite fittings and doing DIY repairs? Once these things hit the market, there really is no excuse for calling a pro to do an easily accessible repair. If you have a skill set that includes some basic mechanical ability, Shark Bites can make a repair pretty easy, and foolproof. Good luck.
