I've recently purchased a hot tub and I'm in the process of building a deck and running electric. This tub can run on a 40A, 50A or 60A circuit, all dependent on what the owner wants or has available. The 40A current draw enables just one of the pumps and the heater to run. 50A set up is both motors at once with no heater and the 60A allows all three to run at once. Your tub may or may not run at 40A or 50A, but it would depend on how it has been set up. If you have wire ran to the tub that will support 50A, your tub may run more components when in use.
Either way, use a GFCI.