AWP Labs · Chemistry
Scaling index
Find out whether water will deposit calcium carbonate scale or dissolve it. Calculates the Langelier Saturation Index and Ryznar Stability Index.
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Langelier Saturation Index
+0.42
Near balanced
Close to saturation. Little tendency to scale or to dissolve calcium carbonate.
- Saturation pH
- 7.18
- pHs
- Ryznar index
- 6.76
- Stable
- Evaluated at
- 2,000mg/L TDS
- Ca 300 · Alk 230
How this is calculated
Saturation pH. pHs = (9.3 + A + B) − (C + D), with A = (log₁₀ TDS − 1) ÷ 10, B = −13.12 × log₁₀(°C + 273) + 34.55, C = log₁₀(Ca hardness) − 0.4 and D = log₁₀(alkalinity).
Langelier index. LSI = pH − pHs. Positive means the water is supersaturated with calcium carbonate and can scale. Negative means it is undersaturated and corrosive.
Ryznar index. RSI = 2 × pHs − pH. Below about 6 the water scales, above about 7 it corrodes.
Assumptions
- Valid for typical waters with pH 6.5–9.5 and TDS up to about 10,000 mg/L.
- For seawater and high-salinity concentrate, the Stiff & Davis index is the better measure.
- Covers calcium carbonate only. Sulfate, silica and barium scales need a separate check.
A preliminary estimate for planning. AWP confirms every figure against your water, site and permit before quoting.
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