Why must metal water pipes be bonded?

Metal water pipes must be bonded primarily to ensure that any ground fault current can be safely directed to ground, which helps prevent electrical shock hazards. When metal water pipes are part of the grounding system, they provide a low-resistance path for electrical faults. If an electrical fault occurs, the bond allows electrical current to flow back to the ground, minimizing the risk that any person or equipment connected to the water system will become a path for electrical current, which could lead to severe injury or death from electrical shock.

While the other options touch on aspects related to water systems or building codes, they do not directly address the critical safety measures that bonding provides against electrical faults. Therefore, bonding metal water pipes enhances the safety of electrical systems by providing a clear and effective way for fault currents to flow safely to ground.