A fan serves to suction combustion gas which has passed through a secondary heat exchanger and emitting combustion gas to the outside of a water heater. A drainage water discharge pipe is connected to the secondary heat exchanger in order to discharge the drainage water produced as a result of recovery of latent heat in the secondary heat exchanger to the outside of the secondary heat exchanger. An air passage pipe is connected to an exhaust box. A Y-shaped pipe joint has a flow path allowing merging of the drainage water discharge pipe and the air passage pipe, and the flow path after merging leads to the outside of the water heater.