The pool and spa will share the circulation pump, filter, heater and sanitizing equipment with accuator valves to change from pool suction to spa suction and pool return to spa return. The spa jets should be run off its own pump with suction from the spa returning to the spa jets. You could also plumb suction from the pool to the spa jet pump with an accuator valve to get more water going over the spill way when not heating the spa (it will cost more to run the jet pump for the extra water but sometimes the extra water looks good for parties or just to impress your neighbor).