In order for a metal underground water pipe to be used as a grounding electrode, it shall be in direct contact with the earth for ______.
a) 5 ft
b) 10 ft or more
c) less than 10 ft
d) 20 ft or more
See answer and applicable Code reference
The correct answer is: b) 10 ft or more
Part III of Art. 250 focuses on the grounding electrode conductor and grounding electrode system. As per Sec. 250.52(A)(1), "A metal underground water pipe in direct contact with the earth for 10 ft or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductor(s) or jumper(s), if installed."