2.) The bonding of metal water piping in the vicinity of separately derived systems.
250.104 Bonding of Piping Systems and Exposed Structural Steel.
(A) Metal Water Piping.(4) Separately Derived Systems. The grounded conductor of each separately derived system shall be bonded to the nearest available point of the interior metal water piping system(s) in the area served by each separately derived system. This connection shall be made at the same point on the separately derived system where the grounding electrode conductor is connected. Each bonding jumper shall be sized in accordance with Table 250.66.
Exception: A separate water piping bonding jumper shall not be required where the effectively grounded metal frame of a building or structure is used as the grounding electrode for a separately derived system and is bonded to the metallic water piping in the area served by the separately derived system.
Example: Any metallic water pipe located in the vicinity served by the separately derived system must be bonded to the grounded conductor connection of the separately derived source. The metal water piping serving an office kitchenette with 120-volt power provided from a nearby transformer must be bonded to the transformer grounded connection.