LSI calculator for pool service
Calculate Langelier Saturation Index from your readings. Enter values, get a verdict and recommended adjustments. Tabulated factors, CYA correction included.
Enter your readings
Readings
Carbonate alkalinity = total alkalinity minus (CYA / 3). PoolStack does this correction automatically. Used in the alkalinity factor lookup.
Result
-0.09LSI
Balanced, ideal
Recommended actions
- Maintain current chemistry.
- Re test next visit.
- pH
- 7.5
- Temp factor
- 0.65
- Ca factor
- 2.00
- Alk factor
- 1.91
- CA 77 ppm
PoolStack auto calcs LSI on every visit
Recommendations come with each reading, no manual lookup.
About this calculator
What LSI tells you
The Langelier Saturation Index estimates whether your pool water is scaling, balanced, or corrosive based on six readings. Numbers above zero trend toward scale on tile, heater elements, and salt cells. Numbers below zero trend toward etching of plaster and corrosion of metal fittings.
Pool service operators target an LSI between minus 0.3 and 0.0. PoolStack auto calcs this on every visit and recommends dosing to move readings into the band, no manual lookup needed.
When the index is off, the chemical dosage calculator works out how much to add to bring pH, alkalinity or calcium hardness back.
How to calculate Langelier Saturation Index (LSI)
Enter six water readings (pH, temperature, calcium hardness, alkalinity, CYA, TDS) and get a scaling, balanced, or corrosive verdict with recommended adjustments.
Enter pH
Type in the current pH reading from your test kit.
Enter water temperature in degrees Fahrenheit
Use the actual pool temperature, not an average.
Enter calcium hardness and total alkalinity
Type in both readings in parts per million from your test.
Enter cyanuric acid and TDS
Type in CYA and total dissolved solids. The calculator applies the CYA correction automatically.
Read the verdict
The LSI value and a plain-English read (scaling, balanced, or corrosive) appear with recommended chemical adjustments.
In PoolStack
Run this in PoolStack
PoolStack runs the whole operation, not just the math.
Every reading is checked against its range in PoolStack's pool service software, with water chemistry, filter cleans and equipment on one record for every pool.
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