Langelier Saturation Index Calculator

The Langelier Saturation Index (LSI) measures whether water is likely to deposit calcium carbonate scale or corrode pipes — critical for managing pool, drinking, and industrial water systems. Enter your water's pH, temperature, Total Dissolved Solids (TDS), Calcium Hardness, and Total Alkalinity to get your LSI value, along with the Water Condition (scaling, corrosive, or balanced), the saturation pH (pHs), and a treatment Recommendation.

Water pH value

mg/L

Measure of dissolved minerals in water

mg/L CaCO3

Bicarbonate alkalinity as CaCO3

Results

Langelier Saturation Index (LSI)

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Water Condition

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pH Saturation (pHs)

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Recommendation

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Frequently Asked Questions

What is the Langelier Saturation Index (LSI)?

The LSI is a calculated index used to predict the calcium carbonate stability of water. It indicates whether water will precipitate, dissolve, or be in equilibrium with calcium carbonate. The index helps determine if water is corrosive or scale-forming.

How do I interpret LSI values?

LSI values below 0 indicate corrosive water that may dissolve calcium carbonate from pipes and surfaces. Values above 0 suggest scale-forming water that may deposit calcium carbonate. Values near 0 (±0.3) indicate balanced water with minimal corrosive or scaling tendencies.

What LSI range is considered ideal for pools?

For swimming pools, an LSI between 0.0 and +0.3 is generally considered ideal. This range provides adequate protection against corrosion while minimizing scale formation on pool surfaces and equipment.

How does temperature affect the LSI calculation?

Temperature significantly impacts LSI calculations because calcium carbonate solubility decreases as temperature increases. Higher temperatures result in higher LSI values, making water more scale-forming. This is why hot water systems often have more scaling issues.

What should I do if my LSI is too high or too low?

If LSI is too low (corrosive), consider increasing pH, alkalinity, or calcium hardness. If too high (scale-forming), reduce pH, lower alkalinity, or decrease calcium levels. Always make gradual adjustments and retest to achieve the desired balance.

Can LSI be used for drinking water systems?

Yes, LSI is commonly used to evaluate drinking water distribution systems. It helps water utilities prevent pipe corrosion and scale formation, ensuring water quality and extending infrastructure life. Balanced water protects both the distribution system and consumers' plumbing.

What water parameters are needed to calculate LSI?

LSI calculation requires five key parameters: pH, water temperature, total dissolved solids (TDS), calcium hardness, and total alkalinity. All measurements should be taken from the same water sample under consistent conditions for accurate results.