A metal underground water pipe in direct contact with the earth for how long qualifies as a grounding electrode?

A metal underground water pipe qualifies as a grounding electrode when it is in direct contact with the earth for a length of at least 10 feet. This requirement is set forth in the National Electrical Code (NEC), which establishes guidelines to ensure safe grounding practices. The reason for the 10-foot length is to ensure adequate conductivity and effective grounding by allowing for a stable connection to the earth. This length helps minimize resistance and provides a reliable path for fault current, enhancing the safety of the electrical system.

The other lengths provided do not meet this specific requirement, as they fall short of the threshold necessary to ensure proper grounding integrity. Thus, having the specified length is crucial for achieving compliance with grounding and bonding standards, ensuring the safety of both equipment and personnel in electrical installations.