Exception: In industrial, commercial, and institutional buildings
or structures, if conditions of maintenance and supervision
ensure that only qualified persons service the installation,
interior metal water piping located more than 1.52 m (5 ft)
from the point of entrance to the building shall be permitted as
a bonding conductor to interconnect electrodes that are part
of the grounding electrode system, or as a grounding electrode
conductor, if the entire length, other than short sections passing
perpendicularly through walls, floors, or ceilings, of the
interior metal water pipe that is being used for the conductor
is exposed.