The present invention relates to a water heater system comprising: a hot water boiler having top, bottom and side walls; a flue connected to the top wall; a burner secured to a side wall of the first housing a combustible feeder connected to the burner; an evaporator having a housing, the housing comprising an outlet, heat exchange elements located in the housing and a water discharge device spaced above the heat exchange elements, wherein the evaporator provides a source of humid air to the burner for increasing the combustion product dew point and to reduce NOx emission when burned; and a beat recovery system connected to the flue wherein the heat is used for heating water used by the water discharge device.
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