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He may be running it at 110V but I'm pretty sure it is what is known as a convertible tub meaning you can run it either way depending on how you jumper it so you'd be able to run it at 220 or 221 (whatever it takes).
My wife is really looking forward to her first soak
Yes, it is convertible: you will need to supply it with two GFI protected circuits. One 30A 220V and one 20A 120V - the easiest way to do this is to purchase a subpanel from a HotSpring dealer. I sell them for around $135, which is a good price even compared to collecting the parts yourself from a home center.