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Calcimator

Corrosion Control Calculator

Calculate the Langelier Saturation Index (LSI) and Ryznar Stability Index for pipe corrosion prevention in drinking water.

Inputs

mg/L as CaCO₃
mg/L as CaCO₃
mg/L
°F

Results

Langelier Saturation Index

-1.01

LSI Interpretation

Highly Corrosive (aggressive water)

Ryznar Stability Index9.22
RSI InterpretationVery Corrosive
Aggressive Index11.1
AI InterpretationModerately Aggressive
Saturation pH (pHs)8.21
Target pH for Balance8.21
Recommended TreatmentpH adjustment (lime/caustic soda) + corrosion inhibitor
Lead/Copper Rule RiskModerate Risk
CaCO₃ Precipitation Potential-25 mg/L
How to Use This Calculator
  1. Enter Water pH from your latest distribution system or treatment plant measurement.
  2. Input Total Alkalinity (mg/L as CaCO₃) and Calcium Hardness (mg/L as CaCO₃) from a water quality analysis.
  3. Enter Total Dissolved Solids (mg/L) and Water Temperature (°C) to complete the water chemistry profile.
  4. Review the Langelier Saturation Index (LSI): negative values indicate corrosive water, positive values indicate scaling tendency.
  5. Check the Ryznar Stability Index (RSI) and Aggressive Index (AI) for additional corrosion characterization.
  6. Use the interpretation outputs to guide pH, alkalinity, or inhibitor adjustments to meet Lead and Copper Rule corrosion control requirements.

How the result changes with Water pH

Water pHLangelier Saturation IndexLSI Interpretation
4.6-3.61Highly Corrosive (aggressive water)
6.1-2.11Highly Corrosive (aggressive water)
7.9-0.31Near Equilibrium
9.41.19Scale-Forming (heavy CaCO₃ deposits likely)

What each input means

Water pH
Measured pH of the treated water.
Total Alkalinity
Total alkalinity measured as calcium carbonate equivalent.
Calcium Hardness
Calcium hardness as calcium carbonate.
Total Dissolved Solids
Total dissolved solids concentration.
Water Temperature
Water temperature at the point of testing.

What each result means

Langelier Saturation Index
Positive = scale-forming, Negative = corrosive.
Ryznar Stability Index
<6 = scaling, 6-7 = stable, >7 = corrosive.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Water pH = 7.2, Total Alkalinity = 80, Calcium Hardness = 100, Total Dissolved Solids = 200 = 5 input(s) provided
  2. Calculate Langelier Saturation Index
    Langelier Saturation Index
    -1.01 = -1.01
  3. Calculate LSI Interpretation
    Highly Corrosive (aggressive water) = Highly Corrosive (aggressive water)
  4. Calculate Ryznar Stability Index
    Ryznar Stability Index
    9.22 = 9.22
  5. Calculate RSI Interpretation
    Very Corrosive = Very Corrosive

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