Which item is not permitted to be used as a grounding electrode?

• A. metal underground gas piping
• B. zinc coated steel
• C. stainless steel
• D. copper pipe larger than the metric designator 21

Answer: (A)

Grounding electrodes provide a reliable path from the electrical system to the earth, so they must be permanent, conductive, and in direct contact with soil to stay effective. Metal underground gas piping is not allowed as a grounding electrode because gas systems aren’t designed to serve electrical grounding, and their continuity can be compromised during maintenance, repairs, or movement of gas lines. This makes them an unreliable and unsafe choice for grounding. In contrast, metal underground water piping and certain metal pipes like zinc-coated steel, stainless steel, or copper that are in direct contact with earth can function as grounding electrodes when installed correctly, since they provide a stable, continuous path to the earth.