1. What is the Langelier Saturation Index?

The Langelier Saturation Index (LSI) is a calculated number used to determine the calcium carbonate saturation level in water. It indicates whether water will precipitate, dissolve, or be in equilibrium with calcium carbonate.

2. How Does the Calculator Work?

The calculator uses the Langelier Saturation Index equation:

Where:

• \( pH \) — Current pH of the water
• \( TF \) — Temperature factor (depends on water temperature)
• \( CF \) — Calcium hardness factor (depends on calcium concentration)
• \( AF \) — Alkalinity factor (depends on total alkalinity)
• 12.1 — Constant representing the negative logarithm of the solubility product of calcium carbonate

Interpretation:

• LSI = 0: Water is perfectly balanced
• LSI > 0: Water is scale-forming (over-saturated with calcium carbonate)
• LSI < 0: Water is corrosive (under-saturated with calcium carbonate)

3. Importance of LSI Calculation

Details: The LSI helps predict whether water will deposit or dissolve calcium carbonate, which is crucial for maintaining pool surfaces, pipes, and equipment. Proper LSI balance prevents corrosion and scaling.

4. Using the Calculator

Tips: Enter the current pH of your water and the calculated factors (TF, CF, AF). The calculator will determine if your water is balanced, corrosive, or scale-forming.

5. Frequently Asked Questions (FAQ)

Q1: What is the ideal LSI range?
A: For most applications, an LSI between -0.3 and +0.3 is considered balanced.

Q2: How do I determine the TF, CF, and AF values?
A: These factors are calculated from water temperature, calcium hardness, and alkalinity measurements using standard tables or calculators.

Q3: What should I do if my LSI is out of range?
A: Adjust pH, alkalinity, calcium hardness, or temperature to bring the LSI into the desired range.

Q4: How often should I check the LSI?
A: For pools, check at least weekly. For industrial applications, continuous monitoring may be needed.

Q5: Does LSI apply to all types of water?
A: The LSI is most accurate for potable water and swimming pools. Other indices may be better for seawater or high-TDS waters.