You can find packaged solutions designed to mix with water to repair a hot tub leak. These solutions are usually blended materials designed specifically to seal hard-to-reach areas such as bathtub piping. Simply drain the tub, remove all filters and fill it up again with water. Turn on the motor, and pour the solution into the suction intake, following the manufacturer's instructions. Keep the water running for 8 hours until the leak is fixed. Drain and clean the hot tub to let the solution cure for 24 hours. Leave the tub for a week for best results.