I can't tell you anything about your place because I haven't seen it ... however ... here's a true story:
My house is built literally into a mountain. It's vintage ~1790. The well was dug (~285') into the mountain in 1973. When I moved in (1988) I replumbed the entire house in CPVC and PVC because the minerals in the water had rotted thru the copper to the point of constant pinholes in the type M copper (heavy wall). The copper was put in in 1973 along with the well. Every last piece is now plastic except a 12" nipple at the (gas) water heater in and out couplings due to the heat. In 1997 I tore out the old fuse box and put in a main breaker panel. The AHJ wanted a #6 to the water heater to ground the water itself. His argument was that there were so many minerals in the water that it became a good enough conductor to cause a problem. He told me that this was a common problem in the area. (Yes, I had the water checked by the county health dept and they declared it safe to drink). It was easier to comply than argue. In 2004 I did my neighbors house and the county still wanted this #6.
