Thanks all. Per response from NFPA, a rod, pipe, or plate electrode that supplements a water pipe is considered a 'single' electrode and has to be 25 ohms or less to earth, or be supplemented. I guess I was just getting hung up by the term 'system' as used in 250.50; and offering the possibility that a 'system' of multiple electrodes might not be interpreted as a 'single' electrode.
