Langelier Saturation Index Calculation:-

As an example, suppose the drinking water supplied to animals has the following analysis. The LSI index is calculated at two temperatures: 25^oC (room temperature) and 82^oC (cage wash cycle). The colder incoming water will warm to room temperature in the manifolds. Residual water in the rack manifold can be heated to 82^oC when the rack is in the cage washer.

• Water Analysis:
  
  • pH = 7.5
  • TDS = 320 mg/L
  • Calcium = 150 mg/L (or ppm) as CaCO₃
  • Alkalinity = 34 mg/L (or ppm) as CaCO₃
    
    
• LSI Formula:
  
  • LSI = pH - pH_s
  • pH_s = (9.3 + A + B) - (C + D) where:
    • A = (Log10[TDS] - 1)/10 = 0.15
    • B = -13.12 x Log10(^oC + 273) + 34.55 = 2.09 at 25°C and 1.09 at 82°C
    • C = Log10[Ca²⁺ as CaCO₃] - 0.4 = 1.78
    • D = Log10[alkalinity as CaCO₃] = 1.53

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• Calculation at 25^oC:
  
  • pH_s = (9.3 + 0.15 + 2.09) - (1.78 + 1.53) = 8.2
  • LSI = 7.5 - 8.2 = - 0.7
  • Hence No Tendency to Scale

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• Calculation at 82^oC:
  
  • pH_s = (9.3 + 0.15 + 1.09) - (1.78 + 1.53) = 7.2
  • LSI = 7.5 - 7.2 = + 0.3
  • Hence Slight Tendency to Scale

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Langelier Saturation Index Calculator

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Langelier Saturation Index (LSI) Calculator

LSI calculator tool helps you determine the scaling potential of the pool water. Using this tool u can get the balancing level for corrosion scaling index point of a pool water.

Formula:

Saturation Index = pH + calchd + totak + tmpc - 12.1

Langelier Saturation Index Calculator:

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Total Alkalinity:	Select Value 5 ppm 25 ppm 50 ppm 75 ppm 100 ppm 125 ppm 150 ppm 200 ppm 250 ppm 300 ppm 400 ppm 800 ppm 1000 ppm
Calcium Hardness:	Select Value 5 ppm 25 ppm 50 ppm 75 ppm 100 ppm 125 ppm 150 ppm 200 ppm 250 ppm 300 ppm 400 ppm 800 ppm 1000 ppm
Temperature:	Select Value 0 °C 3 °C 8 °C 12 °C 16 °C 19 °C 24 °C 25 °C 26 °C 27 °C 28 °C 29 °C 30 °C 31 °C 32 °C 33 °C 34 °C 35 °C 36 °C 37 °C 38 °C 39 °C 40 °C
Measured pH:
Langelier Saturation Index:

Interpreting the LSI:

• The ideal LSI value is 0, indicating that the water is perfectly balanced. If the SI value from the equation lies between +0.3 and – 0.3 then the water is also considered balanced and no adjustments are needed.

• Higher than +0.3 indicates the probability of the water to be scale-forming (over-saturated with minerals). The higher the LSI value, the greater the chance of scale formation.

• Lower than –0.3 indicates the probability of the water to be corrosive. The lower the SI value, the greater the danger of corrosion.

• Like pH, the LSI value is logarithmic, meaning that a difference of 1.0 equates to a difference of ten times in reality. A Saturation Index of -2.0 is ten times more corrosive than an SI of –1.0.