I just put one in last week. There was a lug on the motor but other than that it was all plastic and self contained; however, a hydromassage tub differs from a self contained hot tub/spa in that the water fill is from a spigot and faucet set not from within the fiberglass tub itself. My local AHJ wanted a bond to the metal parts of the spigot/faucet set. I'm not sure I agree with him technically, but his theory (NEC required or not) was sound so I didn't argue ... besides the #8 solid cost me a whole $3.54 (including tax and the clamp) and took 15 min to install.
