Is it because moisture or minerals trickle down from the hot water line where it is not protected by the concrete and plastic sleeve?What about the premise that copper corrosion is caused by minerals and/or ph imbalance from anywhere under the slab, which would seem to make any section of copper pipe susceptible?
the original copper loops had hard plastic pipe protecting the copper it has now degredated to whatever the plumber feels like! water heater supply pipes have a die-electric union, they may be getting grounded by the gas lines combined with the heating more electrolisys is taking place, probably eve more so on electric heaters. ( good guess )?
