i already posted the why's.
its a UL listed spa, my locale does not require bonding beyond what manufacturer has done. this means the water be gnd'd or bonded to the "bonding lug" the spa has.
there can in fact be a voltage generated by the free ions in the soup mix of chemicals in the water, and since the water from top to bond lug is a "variable resistor" i can measure a voltage diff.
i am more curious to know actual resistance, and for this i need to do a current test from water to bond lug.
but as you can see, the bonding doesnt completely fall in alignment with the definition of bonding, etc. the water should be at same potential as everything it is bonded to, but obviously wont be if the soupy battery (water) has resistence between it and the out or water bonding lug, etc.
I don't see the point of the test other than the OP ensuring the realization that the bare minimums of the NEC do not necessarily prevent someone from getting shocked. After all, none of the plumbing in most hot tubs is metallic anyway and water is not a reliable conductor of current...hence bonding to begin with.
plumbing? why would you worry about plumbing? almost every manufactured spa (if not all) has a heater that is a metal, that metal must be gnd'd, and the very conductive water touches the heater.