The Langelier Saturation Index (LSI), published in 1936, has been the standard saturation and scaling indices employed in the water treatment industry. It has since been deemed as overly conservative when applied to industrial applications, being a poor predictor of actual calcium carbonate deposition in industrial water systems therefore leading to an over-dose of chemical inhibitor and increased costs. This article reviews LSI and describes an innovative methodology for quantifying the precipitation of individual mineral species.