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Langelier Saturation Index (LSI) Calculator

Determine whether water will scale or corrode by comparing its pH to the calcium-carbonate saturation pH (pHs). Enter the five parameters below for an instant Langelier Saturation Index and Ryznar Stability Index, with interpretation. For cooling water, RO feed, boiler make-up and potable distribution.

Water analysis

Result

Saturation pH (pHₛ)
Langelier Index (LSI)
Ryznar Index (RSI)
LSI: <0 corrosive / undersaturated (dissolves protective scale) · ≈0 balanced · >0 scaling (CaCO₃ tends to precipitate). RSI: <6 scaling · 6–7 balanced · 7–8 corrosive · >8.5 severely corrosive. Indices are indicative only — confirm against a full water analysis and treatment objectives.