quote; then what has happened is the metal water pipe is just energized and should a plumber have to repair the metal water pipe we have just put him in danger.
That would only occur if there were an additional problem in the system, such as a failed neutral in the utility's feed. Then, the piping would function as the neutral UNTIL the plumber "broke" the continuity. I had it happen many times years ago. In Chicago, when we separated a water line, we NEVER used our hands. We hit the pipe with a wrench to see if there was a spark between the two pieces. One time, everything in the house that was turned on burned out when I disconnected the water line to the water heater. I have also been walking through a house, or in one case UP TO THE TRAILER, when my TicTracer went off indicating that some metal object was energized. Usually, the occupants did not know of the hazard because they could not touch the object and a "ground source" at the same time.