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 a tendency to remove existing calcium carbonate protective coatings in pipelines and equipment. No potential to scale, the water will dissolve CaCO₃.

RSI ≤ 6

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

6 < RSI < 7

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

LSI ≥ 7

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