Saturation Index
A saturation index is a calculated value predicting whether pool water will dissolve minerals (negative index) or deposit them as scale (positive index).
Definition
A saturation index is a calculated value predicting whether pool water will dissolve minerals (negative index) or deposit them as scale (positive index).
Typical Values: LSI target: -0.3 to +0.3
In Plain Language
The Langelier Saturation Index (LSI) is the standard saturation index for pool water. The Ryznar Stability Index (RSI) is another version that uses slightly different interpretation criteria. Both measure the same fundamental tendency of water to corrode or scale. The LSI is the more widely used in the pool industry.
Why It Matters
Saturation indices provide a unified way to assess water balance accounting for the interplay of all balance parameters simultaneously.
Typical Values
LSI target: -0.3 to +0.3
Last reviewed: 2026-06-01