Expert Verified Updated: March 2026

Langelier Saturation Index (LSI) Calculator

Calculate the LSI to determine if your pool water is corrosive, balanced, or scale-forming.

Quick Conclusion
The Langelier Saturation Index (LSI) Calculator provides instant dose calculations for pool maintenance, helping you maintain perfect water balance and extend equipment life.

Technical Comparison

LSI ValueWater StatusAction
< -0.3CorrosiveAdd Calcium/Base
-0.3 to +0.3BalancedMaintain
> +0.3ScalingAdd Acid

Protect Your Finish

Water with a negative LSI is 'hungry' and will eat away at plaster, tile grout, and metal parts.

Actionable Steps

Understanding LSI

LSI is a mathematical formula that predicts if water will deposit calcium (scaling) or dissolve it (corrosion). Aim for -0.3 to +0.3.

⚠️

Safety Warning: Saltwater pools often have higher Scaling tendencies due to higher pH local to the salt cell.

Pro-Tip

The 'TFP' method focuses on FC/CYA ratio, but the LSI is the ultimate judge of whether your water is literally 'eating' your pool surface.

Frequently Asked Questions

What is balanced?

0.00 is perfectly balanced, but anything within 0.3 offset is acceptable.

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