Index Value

Water Condition

LSI > 0

Water is supersaturated with respect to calcium carbonate (CaCO₃) and scale forming and CaCO₃ precipitation may occur.

LSI = 0

Water is considered to be neutral. Neither scale-forming nor scale removing. Saturated, CaCO₃ is in equilibrium. Borderline scale potential.

LSI < 0

Water is under saturated with respect to calcium carbonate. Under saturated water has tendency to remove existing calcium carbonate protective coatings in pipelines and equipment. No potential to scale, the water will dissolve CaCO₃.

RSI, PSI ≤ 6

Supersaturated, tend to precipitate CaCO₃. The scale tendency increases as the index decrease.

6 < RSI, PSI < 7

Saturated, CaCO₃ is in equilibrium. The calcium carbonate formation probably does not lead to a protective corrosion inhibitor film.

RSI, PSI ≥ 7

Under saturated, tend to dissolved CaCO₃. Mild steel corrosion becomes an increasing problem.