When installing a tub into the ground (making a pit for it), the following considerations need to be addressed.
1) The pit needs to provide working space around the tub for making plumbing connections and for servicing. Typical radius should be 1 food more than the radius of the tub.
2) The equipment (pump, heater, filter) is ideally at the same level as the hot tub base, and a nook for it also must be carved out.
3) The pit must be designed to be draining, otherwise it will fill up with water during a heavy rain.
4) If the equipment is above ground, different self priming pump is needed, a check valve and the supply piping must be constructed differently.