In Brazil, for the majority of open recirculating systems, make-up water contains a low dissolved solids index and its main contaminants are aluminum and iron. The first one derives from raw water clarification process leakage; the latter may have the same origin and/or may be a product of equipment and lines corrosion. Iron and aluminum form a compound of low solubility product that may seriously affect the heat transfer. Considering these characteristics, treatment programs were developed. The high efficiency of these programs is due to "high performance" dispersants that assure a perfect performance for corrosion inhibitors and biocides. This paper shows four years well succeeded programs used at a crude refinery where-own process contamination (sulphide, hydrocarbon) generally effect negatively any treatment program applied.