If you have a hydro massage tub and the plumbing is all plastic, is the # 8 solid copper wire needed? Is so, where is it going to? What if you have a brass water spout flowing water into the tub? Any thoughts?
It is needed incase the moter has a short and the casing becomes hot without tripping the breaker. There should be a lug on the side of the motor itself to attach to and then, depending on your jurisdiction, to the cold water and/or the EGC.
I had a home inspector write up a hydromassage tub saying it was not bonded. The tub was inside and the motor was outside. All the plumbing was plastic including the drain. The only two metal objects in the motor area were the motor/pump assembly and the junction box. So I bonded these two together. What else was there to do? Now if the water supply pipes were metal, with the motor outside the building, would you have to bond the piping to the motor even though a person could never contact both at the same time??? These are the house plumbing pipes I am referring to, not the recirculation piping to the pump.
There are some AHJ's around here making the EC run a #8 wire all the way back to the service panel. However if there is a small piece of metal pipe attached to the spout, do you think it should be bonded to the motor? Or is it small enough to let it slide, and not bond it at all?
As George pointed out a HM tub is not a spa and a spout is not a system so you probably don't have to bond it. On the other hand if a few feet of wire would make you feel better you could. The AHJ who wants to make the 8ga bond part of grounding system is wrong, at least the way I understand the issue. Our AHJs don't even like to admit grounding current could flow to the pool, and that is exactly what will happen. That huge Ufer, full of water, out there is going to be the most effective electrode on the property.
Mine got bonded back to the panel with a #8 anyway simply because the spa and pool are bonded and the spa heater has an 8ga EGC along with the pool light #12, 4 pumps with their #12s and the incidental bonding of all the electrical that is attached to the screen cage which is part of "the grid". I don't think you can have too much bonding.