Must be GFI protected, of course, and there has to be a disconnect more than 6 feet, but not more than 10 feet away from the inside of the tub wall. This is so the tub pumps can be turned off if someone gets stuck on the bottom suction port. (it happens)
There must be a GFI outlet within a certain distance, I believe it is 15 feet. I usually buy the GE disconnects with the GFI 50 amp 2 pole already in it. They're pretty affordable over other brands. The biggest mistake everyone makes is they take the neutral wire to the neutral bar and the breaker will just keep tripping. The neutral wire goes to the breaker. There are a few tubs that don't use a neutral -- pull one anyway, as someone mentioned, you may need it later. I would also used sealtite/ liquidtite conduit. It's tough, and rated for direct burial.
I totally disagree that electrical testing is easy. I've been taking them for 18 years and haven't taken an easy one yet.
Colorado master electrician
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