It would be worth noting that more and more civil and plumbing types are using/allowing the use of plastic (non-metallic) piping for the underground portion of the domestic and fire water services into many commercial buildings, with maybe only the underground elbow and riser to above the floor slab being metal. NFPA 70 does not allow the use of water service piping as an electrode unless there is at least 10 feet of metal piping underground, and in contact with earth. We are discovering numerous instances where the contractor bonded the grounding electrode conductor to the incoming water piping, only to discover there was no metal piping under the slab, except the riser (way less than the required 10 feet). As the use of plastic piping is becoming the "norm" vs. the exception, more thought should be given by the code writing committees to rewording article 250, with more warnings and more emphasis on the other electrodes. And, designers must take a more agressive stance in coordinating this issue with the plumbing and civil designers, to resolve this during design instead of after the installation is complete and unsafe (when the contractor did what he is "told" or what showed on the drawings vs. doing the right thing).