"Additional wording was also added to 250.52(A)(7), which now allows you to use underground metal well casings as a grounding electrode. This rule change may be a blessing in disguise for the effectiveness of the grounding electrode. Consider a metal well casing, which may be 4 to 8 inches in outer diameter, driven to depths between 75 to 400 feet, in direct contact with an underground water supply and moist soil. Does it get any better than this? It may arguably be the most effective ground electrode of any of the choices listed in 250.52(A)(1) through (A)(7).
This revision permits the use of this electrode ? provided that it's not effectively bonded to a metal water pipe. For many installations, where PVC water piping materials are used to connect the well casing to the structure, this may be the most effective electrode you'll ever find.
But be mindful of the requirements of 250.50 when working with well casings. If any of the electrodes listed in sections 250.52(A)(1) through (A)(6) are present, you must consider them primary electrodes and bond them together to form the grounding electrode system. In this case, the metal well casing is an electrode that supplements the primary electrodes noted in 250.52(A)(1) through (A)(6)."
JJ
