The Langelier Saturation Index (LSI) is used to predict the calcium carbonate stability of water, helping to determine whether water will precipitate, dissolve, or be in equilibrium with calcium carbonate. The LSI is interpreted as follows:

LSI Interpretation:

1. LSI = 0:

   • Balanced Water: The water is considered balanced. It is neither corrosive nor scale-forming. This is the ideal situation where the water is in equilibrium with calcium carbonate, meaning there is no tendency for the water to either deposit calcium carbonate scale or to dissolve calcium carbonate from surfaces.

2. LSI > 0:

   • Positive LSI (Supersaturated): The water is supersaturated with calcium carbonate, meaning there is a tendency for calcium carbonate to precipitate out of the water and form scale on pool surfaces, pipes, and equipment. The higher the LSI, the greater the scaling potential.

3. LSI < 0:

   • Negative LSI (Undersaturated): The water is undersaturated with calcium carbonate, meaning it is likely to be corrosive. This can lead to the dissolution of calcium carbonate from pool surfaces, pipes, and equipment, which can cause damage over time. The lower the LSI, the greater the corrosive potential.

Ideal LSI Range for Pools:

• Target Range: Generally, an LSI between -0.3 and +0.5 is considered acceptable for most pools. This range indicates that the water is slightly balanced, with minimal risk of scaling or corrosion. Higher is better within the ideal target range.

• Perfect Balance: An LSI as close to 0 as possible is ideal, as it represents perfectly balanced water.

Maintaining your pool's LSI within this range helps protect your pool surfaces and equipment from the negative effects of either scaling or corrosion, ensuring a longer lifespan for your pool and better water quality for swimmers.