Pool Langelier Saturation Index (LSI)

The Langelier Saturation Index (LSI) is a formula used to determine if pool water is corrosive, balanced, or scaling.

Understanding Langelier Saturation Index (LSI)

The Langelier Saturation Index (LSI) is a measurement used to assess the balance of pool water by analyzing its potential to cause scaling or corrosion. It is calculated using several key water chemistry parameters, including pH, alkalinity, calcium hardness, total dissolved solids (TDS), and water temperature.

How to Calculate LSI

LSI is determined by applying the following factors into a specific formula:

  • pH: A measure of how acidic or basic the pool water is.
  • Total Alkalinity (TA): Helps maintain pH stability in pool water.
  • Calcium Hardness: The level of dissolved calcium in pool water.
  • Water Temperature: Warmer temperatures increase scaling potential.
  • Total Dissolved Solids (TDS): Affects water balance and clarity.

Interpreting LSI Results

  • LSI < -0.3: Water is corrosive and may damage pool surfaces and equipment.
  • LSI between -0.3 and 0.3: Water is balanced and properly maintained.
  • LSI > 0.3: Water is likely to cause scale formation on pool surfaces and plumbing.

Maintaining Balanced LSI

Regularly testing and adjusting pool water chemistry can help keep LSI within the recommended range, preventing both corrosion and scale formation.

Related Terms

  • pH – A measure of how acidic or basic the pool water is.
  • TA (Total Alkalinity) – Helps maintain pH stability in pool water.
  • Calcium Hardness – The level of dissolved calcium in pool water