Depends. A repipe simply means that your current pipe supply lines have a problem that needs to be addressed. Do copper pipes need to be replaced, sometimes, especially if they are installed incorrectly, or if you have a highly corrosive water quality in your area. A good water system would include water treatment, and pressure regulators with the correct type of piping to ensure that the water pipe last for the longest possible period. I have seen copper repipes last 20 plus years with no problems and some only 1 year because of poor installation practices.
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4500 to 9000 is to be expected
Yes, if you're talking about a water softener, you can use copper piping.
The process of copper re-piping is basically replacing all iron piping in a home with that of copper piping. Unless a homeowner knows how to do plumbing applications, a professional plumber should be hired.
Copper, although plastic piping is preferred nowadays.
Copper piping and wiring and not interchangable.
The question si superfluous as copper piping is NOT used in water wells.
No, however, if copper pipe is going to be chased into the wall and plastered over, you need to use the highest graded copper. (class 2 or 3)
you solder or braze it
No it will not poison you. Copper piping is used extensively in Medical Gas applications. "TYPE L" signifies the wall thickness of the piping.
Chlorination of the copper piping, don't go to strong of a chlorine solution.
1- The piping must be supported with clevis hangers with a metal compatible to copper to prevent electrolytic action2- The spacing between hangers must support the piping from sagging or placing stress on the threaded joints