A passive heater for heating a drainage tube, the passive heater including: an elongated flexible thermal conductor including a first end and a second end, wherein the first end is configured to be disposed in contacting relationship with a heat source and at least a portion of the elongated flexible thermal conductor is configured to be disposed in contacting relationship with a portion of the drainage tube; and an eyelet disposed on the first end, the eyelet configured to facilitate the securement of the elongated flexible thermal conductor to the heat source, wherein the first end is configured to receive heat and transmit it along the elongated flexible thermal conductor to increase temperature of the portion of the drainage tube to prevent freezing of a fluid through the drainage tube.