Please read 250.50. It requires the water piping system to be used as a grounding electrode (assuming it is in contact with the earth for 10 ft or more) and another grounding electrode. If the additional grounding electrode is a driven electrode, a maximum of 25 ohms must be met or a second one must be driven no closer than 6 ft to the first one.
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Charlie Eldridge, Indianapolis,
Utility Power Guy