Code Q&A

Oct. 20, 2011

Q. When a metal water pipe is used as a grounding electrode, is the concrete encased electrode satisfactory as the supplemental electrode, or is a ground rod still required?

Mike Holt

Q. When a metal water pipe is used as a grounding electrode, is the concrete encased electrode satisfactory as the supplemental electrode, or is a ground rod still required?

A. When an underground metal water pipe grounding electrode is present [250.52(A)(1)], it must be supplemented by one of the following electrodes [250.53(D)(2)]:

Metal frame of the building/structure electrode [250.52(A)(2)]
Concrete-encased electrode [250.52(A)(3)]
Ground ring electrode [250.52(A)(4)]
Ground rod electrode meeting the requirements of 250.52(A)(5)
Other listed electrodes [250.52(A)(6)]
Metal underground systems, piping systems, or underground tanks [250.52(A)(8)]

The termination of the supplemental grounding electrode conductor must be to one of the following locations (see Figure):

Grounding electrode conductor
Service neutral conductor
Metal service raceway
Service equipment enclosure

Exception: The supplemental electrode is permitted to be bonded to interior metal water piping located not more than 5 ft from the point of entrance to the building/structure [250.68(C)(1)].

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.