To what can the metal water piping system be bonded according to NEC guidelines?

According to the National Electrical Code (NEC), the metal water piping system must be bonded to electrodes. This is essential because bonding creates a low-resistance path for fault currents, which helps to minimize the risk of electrical shock and ensures that the electrical system operates effectively. By bonding the water piping to electrodes, it provides a reference point for earth ground and enhances the grounding system's overall safety.

In contrast, mechanical grounding rods, electrical transformers, and grounding plates do not serve the same purpose in the context of bonding the water piping system. While grounding rods are used to establish a connection to the ground, they are not specifically indicated for bonding water piping systems. Similarly, electrical transformers function in power distribution and do not relate directly to the bonding requirements of water piping. Grounding plates, while they contribute to the grounding system, do not apply in the direct bonding of the piping as specified by NEC guidelines. Thus, bonding to electrodes is the correct approach for ensuring compliance and enhancing safety.