How many grounding electrodes are required if a building has an underground metal water pipe?

The requirement for grounding electrodes when a building has an underground metal water pipe hinges on the specific conditions set forth in the National Electrical Code (NEC). If the underground metal water pipe is in direct contact with the earth and is at least 10 feet long, it qualifies as a grounding electrode. In this scenario, only one grounding electrode is needed.

This is crucial because the grounding electrode system is designed to establish a low-resistance path to ground, which helps ensure electrical safety by facilitating the operation of overcurrent devices and limiting voltage surges. Since the underground metal water pipe serves this purpose effectively when it is in contact with the earth, it is sufficient on its own as a grounding electrode. The requirement to have just one grounding electrode simplifies the grounding process for structures using this method.