portable spas in the nature of heated and chilled pools; a water temperature control system and portable spa sold as a unit, the water temperature control system comprised of a water heater, a water chiller, a controller and a thermostat; a water temperature control system comprised of a water heater, a controller and a thermostat, for use with a portable spa; a water temperature control system comprised of a water chiller, a controller and a thermostat, for use with a portable spa