Supplemental Electrode—One or Two Required?

摘要

Metal underground water pipes have been used as zero reference points or natural electrodes for electrical systems supplying buildings and other structures for many years without problems. When a metal water pipe deteriorated with age or from corrosion, a new metal water pipe was installed in its place. With the introduction of nonmetallic water piping systems in new construction and the replacement of deteriorated metal water pipes with nonmetallic ones for existing buildings, underground metal water pipes should not be relied upon as the only electrode for the electrical installation.