Looks like there is an optional rapid heater for these things,
own separate GFCI circuit, in addition to the circuit for the pump.
"First, I'm wondering first if the heater is a must-have kind of thing.
That is, isn't filling it with hot tap water enough? Or perhaps
it depends on how long you plan to sit in it, since the water will be
It isn't a must have or they wouldn't sell them without. Lots of them
don't have heaters. It does depend on how long you will stay in the
tub, how much additional hot water is available to put some more in to
keep it warm, how much you mind having to fiddle with adding water,
"Second, why is a second circuit needed?"
Because it takes enough amps to run the heater that it should be on
it's own circuit.
Second, why is a second circuit needed?