The power ("On/Off") switch on a hot tub activates the motor that pumps water through the jets at high pressure to create the "hot tub" experience. If you own a hot tub and your switch is defective, you can replace it using the similar procedures that apply to a power switch on any appliance, with minor differences. You'll find a replacement On/Off switch at a pool/spa supply store or at select hardware stores. It's possible you already have the tools you'll need to install the switch.
Go to the fuse box and trip the circuit breaker to discontinue the electric power to the hot tub.
Open the lid of the hot tub's electric junction box -- this typically is found next to the hot tub if it is being used outdoors and may require screws to be removed first using a Phillips screwdriver. Trip the main power lever (from "On" to "Off") inside the box and close the lid. Ignore all of Step 2 if the hot tub is being used indoors, as there is no electric junction box.
Open the side panel at the bottom of the hot tub -- you may need to remove screws first with a Phillips screwdriver. Turn the water valves inside the panel's compartment clockwise until you feel resistance.
Remove the screws from around the switch using a Phillips jeweler's screwdriver or a Torx screwdriver -- the type of screwdriver you'll need will be dictated by the model of the hot tub. Place the screws in your pocket so that they don't get lost. Pull the switch panel from around the switch. Place the switch panel aside.
Remove the screws from each side of the switch using either a jeweler's Phillips screwdriver or a Torx screwdriver. Place the screws in your pocket so they don't get lost. Pull the switch out from the hot tub.
Loosen the screws on the back of the switch with the jeweler's Phillips screwdriver. Unwind the wires from the screws, taking note of where each wire is wrapped. Dispose of the switch in a proper manner.
Loosen the screws on the back of the replacement switch with the jeweler's Phillips screwdriver. Wind the ends of the wires around the screws in the same manner as they were on the switch that you have disposed of. Tighten the screws.
Place the replacement switch in the hot tub so that it occupies the same position as the other switch did. Attach the switch screws that you placed in your pocket to the switch. Place the switch panel over the switch. Reattach the panel screws.
Rotate the water valves counterclockwise four to five times. Place the side panel back on the hot tub and reattach any screws. Trip the switch in the electric junction box back to "On" and close the lid and reattach any screws -- if there is no electric junction box, ignore this step. Restore power to the hot tub from the fuse box.