Maker Label Studio

Pool Langelier Saturation Index (LSI) Calculator

Calculate swimming-pool water balance to prevent corrosion or scaling using the standard Langelier index method.

Water Parameters

LSI Results

Saturation Index (LSI)
0.00
Balanced
Temperature Factor (TF)0.00
Calcium Factor (CF)0.00
Alkalinity Factor (AF)0.00
TDS Factor (TDSF)0.00
Adjusted Alkalinity0 ppm

System Self-Tests

Click "Run Self-Tests" to verify calculations against standard expected outcomes.

About the Pool Langelier Saturation Index (LSI) Calculator

The Pool Langelier Saturation Index calculator helps aquatics facility managers and pool technicians perfectly balance water chemistry. By calculating the LSI from current water tests, you can prevent corrosive degradation of pool surfaces or the formation of damaging calcium carbonate scale on expensive filtration equipment.

How it works

  1. Test your water and enter the current pH, temperature, and calcium hardness.
  2. Input the total alkalinity and total dissolved solids or cyanuric acid levels to adjust for carbonate alkalinity.
  3. Review the LSI score, targeting a zero or slightly positive number for ideal water balance.

Frequently asked questions

What does a negative LSI value mean for my pool?

An LSI value below -0.3 indicates corrosive water. The water is under-saturated with calcium and will begin dissolving plaster walls, grout, and concrete pool shells.

How does temperature affect the Langelier Saturation Index?

Unlike most substances, calcium carbonate becomes less soluble in warmer water. As pool temperature rises, the LSI increases, raising the risk of scale formation.

Do I need to adjust for Cyanuric Acid when calculating LSI?

Yes. Cyanuric acid contributes to total alkalinity but does not protect against pH changes. You must subtract a portion of your cyanuric acid reading from total alkalinity for an accurate LSI.

Can I rely on LSI for salt water pools?

Absolutely. Salt water pools typically have high Total Dissolved Solids. High TDS lowers the LSI, making accurate calculations critical to prevent corrosion of the salt cell.

References