ICC Residential Electrical Inspectors Practice Exam

Which of the following is prohibited from being used as a grounding electrode?

1. Metal water piping

2. Underground gas piping system

3. Metal building structures

4. Concrete-encased electrodes

The correct answer is: Underground gas piping system

The correct answer is that an underground gas piping system is prohibited from being used as a grounding electrode due to safety concerns and the inherent properties of gas piping systems. Gas piping systems are not intended to carry electrical currents, and using them as grounding would create serious safety hazards. If electrical faults occur, grounding through gas piping could result in stray currents that may provoke sparks, increasing the risk of fire or explosion. In contrast, metal water piping, metal building structures, and concrete-encased electrodes are all recognized and approved methods for grounding in electrical systems. Metal water piping is directly connected to the earth and is often used as a grounding electrode, while metal building structures provide a robust grounding path. Concrete-encased electrodes are effective due to their size and permanent installation, ensuring a stable grounding path over time.