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Produced Water Ion Balance / TDS / SAR Calculator

API RP 45 Water Analysis Computations

Compute TDS, charge balance, hardness, alkalinity, conductivity, SAR, and brine density from a produced-water cation/anion analysis. Charge balance > ±5% flags an incomplete or erroneous analysis. SAR + hardness drive reuse / injection suitability.

Cations (mg/L)

Anions (mg/L)

Conditions

°F

Key Equations

Charge balance:

CB(%) = 100 · (Σ catmeq − Σ anmeq) / (Σ catmeq + Σ anmeq)

Hardness (CaCO₃):

H = 2.5·[Ca²⁺] + 4.12·[Mg²⁺]

SAR (irrigation):

SAR = [Na⁺] / √(([Ca²⁺] + [Mg²⁺]) / 2) (meq/L)