Langelier Saturation Index (LSI) Water Scaling & Corrosivity Calculator

Determine if water is balanced (−0.3 to +0.3), corrosive (<−0.3), or scale-forming (>+0.3).

Langelier Saturation Index (LSI)
-0.05 LSI
Calcium Carbonate Saturation pH (pH_s) 7.55 pH_s
Ryznar Stability Index (2·pH_s − pH) 7.6 RSI
Margin from Ideal 0.0 LSI -0.05 pts
Inputs
pH
Measured water pH.
°C
Water temperature in °C.
ppm
Calcium hardness as ppm CaCO₃.
ppm
Total carbonate alkalinity as ppm CaCO₃.
ppm
Total Dissolved Solids (TDS) in ppm.
Results & Graph
Langelier Saturation Index (LSI)
-0.05 LSI
Calcium Carbonate Saturation pH (pH_s)
7.55 pH_s
Ryznar Stability Index (2·pH_s − pH)
7.6 RSI
Margin from Ideal 0.0 LSI
-0.05 pts

Langelier Saturation Index (LSI)

Graph 1 • Water Ph Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
-3.8 LSI 0.1 LSI 4.0 LSI 50%: -3.8 LSI -3.8 50% 75%: -1.92 LSI -1.9 75% 100%: -0.05 LSI -0.1 100% 125%: 1.83 LSI 1.8 125% 150%: 3.7 LSI 3.7 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Langelier Saturation Index (LSI) -0.05 LSI Calcium Carbonate Saturation pH (pH_s) 7.55 pH_s Ryznar Stability Index (2·pH_s − pH) 7.6 RSI Margin from Ideal 0.0 LSI -0.05 pts
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Langelier Saturation Index (LSI)-0.05 LSICalcium Carbonate Saturation pH (pH_s)7.55 pH_sRyznar Stability Index (2·pH_s − pH)7.6 RSIMargin from Ideal 0.0 LSI-0.05 pts
Summary: Saturation pH (pH_s) is 7.55, giving an LSI of -0.05 (Balanced (−0.3 to +0.3)).
Summary: Saturation pH (pH_s) is 7.55, giving an LSI of -0.05 (Balanced (−0.3 to +0.3)).
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Formula & Mathematical Methodology: Langelier Index (LSI) Reference Equation

pHs = (9.3 + ATDS + BTemp) − (CCalcium + DAlkalinity)
LSI = pH − pHs
pH_s = (9.3 + A_TDS + B_Temp) − (C_Calcium + D_Alkalinity); LSI = pH − pH_s
  • waterPh: Water Ph (pH)
  • waterTempCelsius: Water Temp Celsius (°C)
  • calciumHardnessPpm: Calcium Hardness Ppm (ppm)
  • totalAlkalinityPpm: Total Alkalinity Ppm (ppm)
  • totalDissolvedSolidsPpm: Total Dissolved Solids Ppm (ppm)

Rounding: Laboratory and clinical equations retain full floating-point precision and round displayed results to 2 decimal places.

Worked Example: Reference Calculation: Langelier Index (LSI)

Determine if water is balanced (−0.3 to +0.3), corrosive (<−0.3), or scale-forming (>+0.3).

  1. Enter the reagent concentrations, assay readings, or clinical laboratory parameters.
  2. Compute the standard formula: pH_s = (9.3 + A_TDS + B_Temp) − (C_Calcium + D_Alkalinity); LSI = pH − pH_s.
  3. Review the primary result, supporting reference intervals, and 3 SVG visualizations.
Result: Evaluates Langelier Index (LSI) via pH_s = (9.3 + A_TDS + B_Temp) − (C_Calcium + D_Alkalinity); LSI = pH − pH_s.

Frequently Asked Questions

What formula is used by the Langelier Saturation Index (LSI) Water Scaling & Corrosivity Calculator?

It computes pH_s = (9.3 + A_TDS + B_Temp) − (C_Calcium + D_Alkalinity); LSI = pH − pH_s and plots three custom SVG graphs showing parameter sensitivity and component breakdowns.

Can I compare different reagent dilutions or lab scenarios side by side?

Yes. Use the "Compare (0/3)" button to pin up to 3 scenarios side by side.

Are entered values stored on any server?

No. Every calculation runs 100% locally in your browser.

Science & Engineering · Analytical Chemistry & Lab Bench

Langelier Saturation Index (LSI) Water Scaling & Corrosivity Calculator: inputs, method, and how to read the result

Determine if water is balanced (−0.3 to +0.3), corrosive (<−0.3), or scale-forming (>+0.3).

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Water Ph: Measured water pH.
  • Water Temp Celsius: Water temperature in °C.
  • Calcium Hardness Ppm: Calcium hardness as ppm CaCO₃.
  • Total Alkalinity Ppm: Total carbonate alkalinity as ppm CaCO₃.

What the calculation includes

With the default values shown, Langelier Saturation Index (LSI) is -0.05 LSI. The calculation follows Langelier Index (LSI) Reference Equation; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Water Ph from 7.5 pH to 8.25 pH changes Langelier Saturation Index (LSI) from -0.05 LSI to 0.7 LSI. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard IUPAC atomic weights, 25°C (298.15 K) reference thermodynamics, and published clinical literature equations.
  • Educational and laboratory reference tool only; clinical scoring calculators do not replace professional medical judgment or institutional protocols.

Scope: IUPAC / NIH Laboratory & Clinical Reference Standard Check the assumptions and limitations against your situation before relying on the estimate.

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