Which of the following are approved grounding electrodes for a dwelling?

• A. Ground rods only
• B. Ground rods, metal water service pipe, and a concrete-encased electrode (Ufer)
• C. Metal water service pipe only
• D. Concrete-encased electrode only

Answer: (B)

The main idea is that a dwelling’s grounding electrode system can use more than one type of electrode to create a reliable path to earth. Approved grounding electrodes include ground rods, metal water service pipes, and a concrete-encased electrode (the Ufer). Each type provides a different route to the earth, and codes allow combining them to reduce impedance and improve fault current dissipation. A ground rod gives a direct earth path, the metal water service pipe can serve as an electrode if it is bonded and in contact with earth, and a Ufer electrode is embedded in concrete that’s in contact with the soil, often offering a very low impedance path. Because a dwelling can meet the grounding requirement with any of these electrodes or a combination thereof, stating that all three types are approved together is correct. This is why the option listing ground rods, metal water service pipe, and a concrete-encased electrode is the right choice.