A method and apparatus are provided for the non-recirculating self-sanitization of a carbon filter (14) in a water pretreatment system (12). The apparatus includes a heat exchanger (50) that can maintain an activated carbon bed (44) of the carbon filter (14) at a desired sanitization temperature during service operation of the pretreatment system (12) where the pretreatment system (12) is providing a pretreated water stream (32.sub.H) for final treatment.