This calculator generates the Langelier Saturation Index (LSI) for a pool or spa. The LSI assesses the overall balance of the water.
What is the pH level of the spa or pool?
What is the average temperature of your spa or pool?
What is the Alkalinity level of your spa or pool?
What is the Cyanuric Acid level of your spa or pool?
What is the Calcium Hardness level of your spa or pool?
What is the Total Dissolved Solids (TDS) level of your spa or pool?
The Saturation Index is:
Interpreting the LSI
The ideal LSI value is 0, indicating that the water is perfectly balanced. If the SI value from the equation lies between +0.3 and – 0.3 then the water is also considered balanced and no adjustments are needed.
Higher than +0.3 indicates the probability of the water to be scale-forming (over-saturated with minerals). The higher the LSI value, the greater the chance of scale formation.
Lower than –0.3 indicates the probability of the water to be corrosive. The lower the SI value, the greater the danger of corrosion.
Like pH, the LSI value is logarithmic, meaning that a difference of 1.0 equates to a difference of ten times in reality. A Saturation Index of -2.0 is ten times more corrosive than an SI of –1.0.