The exceptions only apply to made electrodes like ground rods. The metal water pipe always requires a grounding electrode conductor or bonding jumper sized per Table 250-66. See 250-66. Don(resqcapt19)
Re: Grounding#79462 12/28/0112:56 AM12/28/0112:56 AM
Frodo, The exception is for a driven pipe electrodemade the same as the way you'd drive a ground rod. It's not for a water pipe. The driven pipe electrode is normally a pretty crummy ground, but if your soil conditions permit, & you can get it below 25 ohms, what the heck.
Scott is right. 250.66 wil not allow the #6 copout on a H20 pipe, because it's seen as the lowest ohmic value, municipal systems being miles long. Ground rods are all for show, try & get below 25 ohms, and your rod separation may well be 50' or more, Ufer's will someday rule, if we can be tipped off before the concrete dudes* pour *knarly bunch that they be...