a water heater including a water container , a combustion chamber adjacent the water heater , a burner associated with the combustion chamber and arranged to combust fuel to heat water in the water container , a flue having an upper portion and a lower portion operatively connected to the combustion chamber and extending through at least a portion of the water container , and a catalytic converter located in the upper portion of the flue . the water heater may also reduce no x and co emissions generated by a water heater having a radiant burner including activating the burner in response to the temperature of water in the water heater as needed , and substantially removing accumulated foreign matter on the burner by periodically activating the burner irrespective of the water temperature for a selected amount of time .