Press on the cover's seam to check if it contains water. Water on the floor can indicate that condensation is leaking between the cover seams and running down the side of the hot tub.
Squeeze a few drops of food coloring into the hot tub to identify large leaks. If you suspect the leak is coming from a particular area, drop the food dye near that area. Shine a flashlight on the tub. Watch to see where the dye flows both inside and outside of the tub, indicating the location of the leak.
Drain the hot tub. Watch it closely to identify the general area where the water is leaking from.
Turn off all power to the hot tub, and inspect all of the tub's connecting parts closely. Feel each part for moisture or drips. In your inspection, include the pump, all fittings, the heater, valves, the shell, pipes and jets. During the inspection, tighten any loose parts and determine if the leaking has stopped once the part is tightened.