How far must interior metal water piping be from the point of entrance to be excluded from the grounding electrode system?

The requirement regarding the distance of interior metal water piping from its point of entrance to be excluded from the grounding electrode system is rooted in electrical safety standards. Specifically, if the metal water piping is located at least 5 feet away from where it enters the building, it is considered remote enough that it does not need to be bonded as part of the grounding electrode system.

The rationale for this distance stems from the understanding that if the piping is closer than 5 feet, it may still be influenced by potential electrical faults or surges entering the building. By maintaining that separation of 5 feet, it minimizes the risk of electrical currents traveling through the water pipes and potentially endangering persons who might come in contact with the plumbing systems or the electrical systems in the building.

This distance is explicitly outlined in electrical codes, such as the National Electrical Code (NEC), which reinforces the importance of proper grounding and bonding to ensure safety within electrical installations. Therefore, this distance is critical for ensuring that the plumbing system does not inadvertently become part of an electrical grounding system, which could pose safety hazards.