calcs.homes
calcs.homes
The Langelier Saturation Index tells you whether your water will corrode metal and plaster, or scale them with mineral deposits. Enter your four readings for a full water-balance check.
Estimate only — assumes typical (non-saltwater) TDS. Salt pools run slightly scaling by comparison.
LSI = pH + temperature factor + calcium factor + alkalinity factor − 12.1, where each factor comes from a standard lookup table based on your reading. A result between −0.3 and +0.3 is balanced. Below −0.3, water is corrosive and will etch plaster and pit metal. Above +0.3, water is scale-forming and will cloud water and coat surfaces with calcium deposits.
Between −0.3 and +0.3 is considered balanced. Closer to 0.0 is ideal — it means water is neither pulling minerals out of your plaster and equipment nor depositing scale onto them.
Adjust whichever input is furthest from typical range — raising pH, alkalinity, or calcium hardness pushes LSI up (toward scaling); lowering any of them pushes it down (toward corrosive). Change one variable at a time and retest.