680-40. Outdoor Installations
A spa or hot tub installed outdoors shall comply with the provisions of Parts A and B of this article except as permitted in (a) and (b).
680-22. Bonding (a) Bonded Parts. The following parts shall be bonded together.
1. All metallic parts of the pool structure, including the reinforcing metal of the pool shell, coping stones, and deck.
(b) Common Bonding Grid. The parts specified in (a) shall be connected to a common bonding grid with a solid copper conductor, insulated, covered, or bare, not smaller than No. 8. Connection shall be made by exothermic welding or by pressure connectors or clamps that are labeled as being suitable for the purpose and are of the following material: stainless steel, brass, copper, or copper alloy. The common bonding grid shall be permitted to be any of the following:
1. The structural reinforcing steel of a concrete pool where the reinforcing rods are bonded together by the usual steel tie wires or the equivalent
2. The wall of a bolted or welded metal pool
3. A solid copper conductor, insulated, covered, or bare, not smaller than No. 8