What is required for the connecting cable from a down conductor to a water pipe?

The requirement for the connecting cable from a down conductor to a water pipe being a main size conductor is based on the need for ensuring sufficient conductivity and safety in grounding systems. Main size conductors are sized appropriately to handle fault currents and provide a low resistance path to ground, which is essential for effective lightning protection. This makes sure that during a lightning event, the energy can safely dissipate into the ground through the water pipe grounding system, minimizing the risk of damage to structures and electrical systems.

Using a conductor that is too small could lead to overheating or ineffective grounding during a fault condition. It is crucial that the conductive path maintains integrity under high current flows, thus adhering to the standard practices concerning conductor sizing in grounding systems is vital for safety and effectiveness in lightning protection.