LSI

LSI & RSI Expert Water Chemistry Calculator

Actual pH Measured water pH (0 – 14) Enter a valid pH between 0 and 14

Temperature

Water temperature Enter a valid temperature

Calcium Hardness mg/L as CaCO₃ Enter a positive value

Total Alkalinity mg/L as CaCO₃ Enter a positive value

Conductivity (EC) µS/cm (micromhos/cm) Enter a positive conductivity value

Water Type / Application Auto-sets the conversion factor

Conv. Factor 0.64

Adjust manually (0.50 – 1.00)

Estimated TDS: — mg/L

Select a water type above or use the slider for custom factor.

LANGELIER SATURATION INDEX

Live

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Enter values to begin

−2 −1 0 +1 +2

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0% 50% 100% 150% 200%+

Conductivity—

Water Type—

Conv. Factor—

Derived TDS—

A (TDS factor)—(log₁₀TDS − 1) / 10

B (Temp factor)—−13.12·log₁₀(T+273) + 34.55

C (Ca²⁺ factor)—log₁₀[Ca] − 0.4

D (Alk factor)—log₁₀[Alk]

pHs (saturation pH)—

RSI = 2pHs − pH—

LSI = pH − pHs —

LSI < −0.30 CaCO₃ undersaturated
Corrosive tendency

−0.30 ≤ LSI ≤ +0.30 Near saturation
Approximately balanced

LSI > +0.30 Scale-forming tendency
Protective film possible

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