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Langelier Saturation Index Calculator

Pool Water Testing Results
Reading Type Value
Total Alkalinity
Cyanuric Acid Reading
Calcium Hardness
Measured pH
LSI Results and Guidance
Langelier Saturation Index:

So how do you use it...?

Enter the water test readings as indicated and click the "Calculate" button.

If the resulting LSI displayed is lower than -0.5 or more than +0.5 you will need to adjust the water condition levels (Alkalinity, pH, Calcium Hardness, Temperature etc) so as to bring the LSI to within the range -0.5 to +0.5 (Balanced).

By entering different values for each water condition level into the calculator you can determine what combination of water condition levels will provide balanced water in your pool and which are suitable for your pool operating requirements.

NEW - Download our LSI Calculator App for Android devices & calculate your LSI on the go

Langelier Saturation Index Notes:

LSI provides a "snap-shot" assessment of pool water balance. Water balance conditions in a pool will change naturally all the time. LSI should be maintained in the range -0.5 to +0.5 to be regarded as acceptably balanced.

LSI can be increased by taking any one or more of the following actions:

  • Increase water temperature
  • Increase pH
  • Increase Total Alkalinity
  • Increase Calcium Hardness

LSI can be reduced by taking any one or more of the following actions:

  • Reduce water temperature
  • Reduce pH
  • Reduce Total Alkalinity
  • Reduce Calcium Hardness

Recommended Water Condition Levels:

pH for all Sanitation Systems 7.2 - 7.6
Total Alkalinity PristineBlue Sanitation System 50 - 90 ppm
  Chlorine/Bromine Sanitation System 80 - 120 ppm
Calcium Hardness PristineBlue Sanitation System 100 - 300 (MAX) ppm
  Chlorine/Bromine Sanitation System Vinyl Pool Liner: 150 - 200 ppm
    Tiled Pool: 200 - 400 ppm


The above calculator assumes that the Total Dissolved Solids (TDS) content of the pool water is maintained BELOW 1000 ppm. If TDS increases above this level then TDS should be reduced by replacing some or all of the pool water with water with lower TDS (usually by using fresh mains water).

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