✦ Pool Chemistry

Pool Saturation IndexCalculator

Calculate your pool’s Langelier Saturation Index (LSI) to keep water balanced and protect your pool surfaces.

Water Parameters

Enter your latest pool test results below.

pH Level 6.5Ideal: 7.2 – 7.89 Total Alkalinityppm 0 ppmIdeal: 80 – 120 ppm400 ppm Calcium Hardnessppm 0 ppmIdeal: 200 – 400 ppm1000 ppm Cyanuric Acidppm 0 ppmIdeal: 30 – 50 ppm200 ppm Salt / TDSppm 0 ppmNon-salt: < 1500 | Salt: ~3200 ppm6000 ppm Boratesppm 0 ppmOptional: 0 – 50 ppm100 ppm

Water Temperature

32°FIdeal: 75 – 85°F104°F

↓LSI < −0.30

Corrosive Water

Permanently etches pool plaster
Dissolves tile grout over time
Rapidly corrodes metal heaters and ladders
Water appears cloudy or metallic

≈−0.30 to +0.30

Balanced Water

Neither corrosive nor scale-forming
Maximizes surface and equipment life
Optimal chlorine efficiency
Clear, comfortable water for swimmers

↑LSI > +0.30

Scale-Forming Water

White calcium deposits along waterline
Cloudy or milky water appearance
Filter clogs and reduced flow rate
Rough surface texture develops

Understanding Each Parameter

pHIdeal: 7.2 – 7.8

The most critical LSI variable. A 0.1 change in pH shifts the LSI by 0.1; lower pH tends toward corrosive and higher toward scale.

Total AlkalinityIdeal: 80 – 120 ppm

Acts as a pH buffer. High TA keeps pH stable but makes it harder to adjust; low TA causes pH bounce.

Calcium HardnessIdeal: 200 – 400 ppm

Calcium is the raw material for scale. Too little leaches calcium from plaster; too much precipitates as white deposits.

Cyanuric AcidIdeal: 30 – 50 ppm

CYA buffers a portion of alkalinity, so the LSI calculation removes about one third of CYA from total alkalinity.

Salt / TDSIdeal: < 1500 or ~3200 ppm

Total dissolved solids affect ionic strength. Salt pools typically run around 3200 ppm.

Water TemperatureIdeal: 75 – 85°F

Warmer water raises LSI; cold water can become corrosive, especially in winter.