Free Chemistry Tool
LSI Calculator
Enter your current water chemistry and get your Langelier Saturation Index instantly. Color-coded result, real-time recommendations, and a full factor breakdown. Built on the Wojtowicz 2001 ion pair corrections.
Enter Your Water Chemistry
0 if no stabilizer or salt pool
Salt pools: ~3000 + 1000 base = ~4000
Factor Breakdown
LSI Reference Scale
Above +0.30 — Scale-FormingCalcium carbonate deposits on surfaces, cell plates, heater coils.
0.00 to +0.30 — BalancedWater is satisfied. Protects surfaces without depositing scale.
?0.30 to ?0.01 — Slightly AggressiveAcceptable. pH ceiling drift will push LSI toward balanced.
Below ?0.30 — CorrosiveWater etches plaster, attacks metal, degrades equipment.
Methodology: This calculator uses the Langelier Saturation Index as adapted for pool water chemistry incorporating Wojtowicz 2001 ion pair corrections. Carbonate alkalinity is calculated by subtracting cyanurate alkalinity (CYA × pH-dependent correction factor) from total alkalinity. TDS factor applied per standard pool chemistry convention. Results are calculated values — field conditions may vary. For professional diagnosis, consult a certified pool operator.
Canonical targets per Pools Scientific standard: pH 7.4–7.6 · TA 80–120 ppm (chlorine pools), 60–80 ppm (salt pools) · CH 200–400 ppm (plaster), 100–150 ppm (fiberglass), 150–250 ppm (vinyl) · CYA 0–50 ppm · LSI ?0.3 to +0.3.
Canonical targets per Pools Scientific standard: pH 7.4–7.6 · TA 80–120 ppm (chlorine pools), 60–80 ppm (salt pools) · CH 200–400 ppm (plaster), 100–150 ppm (fiberglass), 150–250 ppm (vinyl) · CYA 0–50 ppm · LSI ?0.3 to +0.3.