Langelier Saturation Index
A composite score indicating whether water is balanced, corrosive, or scale-forming.
Definition
The Langelier Saturation Index (LSI) is a mathematical model that combines pH, temperature, calcium hardness, total alkalinity, and TDS into a single balance score. A score of 0 means water is perfectly balanced for calcium carbonate. Negative values (below −0.3) indicate corrosive water. Positive values (above +0.5) indicate scale-forming water. The LSI is the final quality check in the water balancing process — if all individual parameters are in range but the LSI is out of range, the combination still needs adjustment.
Quick Facts
- Ideal Range
- -0.3 to +0.5
- Units
- dimensionless
- Also Known As
- LSI, Langelier Saturation Index, saturation index, Langelier index, water balance index
Relationships
Outgoing Relationships
- calculated by → formula-09
- explained by → glossary/langelier-saturation-index
- causes → Scaling
- causes → Corrosion
- measured by → pH
- measured by → Total Alkalinity
- measured by → Calcium Hardness
- measured by → Temperature
Incoming Relationships
- part of ← pH
- part of ← Total Alkalinity
- part of ← Calcium Hardness
- references ← Taylor Technologies