Services, Grounding & BondingQuestion 50 of 120
When a metal underground water pipe is used as a grounding electrode, what else is required?
a.It must be bonded to the gas piping system as the supplement
b.No supplement is required if the pipe is longer than 20 feet
c.It must be supplemented by an additional electrode of a type identified in 250.52
d.It may be used only if the resistance to earth is 25 ohms or less
Explanation
A water pipe electrode is never allowed to stand alone because plastic repairs or dielectric fittings can silently disconnect it from earth, so it must always be supplemented by another qualifying electrode such as a rod or a concrete-encased electrode. Pipe length does not remove the requirement, gas piping is bonded but is not permitted as an electrode, and the 25-ohm test applies to rod, pipe and plate electrodes.
Law Reference: 2023 NEC §250.53(D)(2)Practice all 120 questions free — no signup required.
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