Abstract: The invention relates to a boiler apparatus and, more particularly, to a boiler apparatus for removing a deposit of frost, snow, ice, or the like on the surface of the windshield or rear window of an automobile or the like vehicle by spraying hot water to melt such deposit. The apparatus has at least one pair of heater tube and by-pass tube. The water in the tank is heated by hot exhaust gas in the heater tube and discharged as hot water from a discharge nozzle. When the water in the tank is discharged after passing through a by-pass tube, the water is not heated and discharged at its as-is temperature. The heater tube is usually disposed in a hollow tube body, and the hollow tube body, with the heater tube, is mounted to an exhaust pipe so that the exhaust gas is discharged after passing through the hollow tube body. Alternatively, it may be mounted in position integrally with the engine or muffler.