George, I see where you are going. If this is a non conductive decking surface, I agree I am not sure how you bond it. I usually hear about the issue being a packaged spa dropped on a concrete or other type of paved deck.
I understood expanding this to the grass but I think they missed something.
Does the 2011 address non conductive decking?
I know that was the usual mitigation, adding a 3' deck around the spa.
Reno I would not be "shocked" if we did see something about bonding the water in homes with electric water heaters and plastic pipe. Most new water heaters do come with steel stub ups that would give you at least 9 sq/on of surface and it is bonded to the EGC but I doubt that would trip a 30a breaker.
I know that copper piping will, because my neighbor had an element open up to the water and it was like a bolted fault.
You could hear water boil for about a second and the breaker tripped.
