Saturation pH and Langelier Index Calculator

Understand Water Balance with the Langelier Index

Pool or spa water may look clear but still be unbalanced. The Langelier Saturation Index (LSI) is a calculated value used to determine whether the water is corrosive, balanced, or scale-forming. It's a key tool to protect your pool equipment, improve bathing comfort, and optimize chemical efficiency.

What is Saturation pH (pHs)?

The saturation pH is the ideal theoretical pH at which the water is in equilibrium with calcium carbonate. It depends on four main factors: Total Alkalinity (TAC), Calcium Hardness (TH), Water Temperature, and Current pH. When the actual pH is too far from this value, issues like scaling, corrosion, or cloudy water can occur.

How to Use This Calculator

This tool lets you instantly calculate the pHs and the Langelier Saturation Index for your pool or spa. Simply enter your measured values for alkalinity, hardness, water temperature, and pH. The calculator will provide the results and indicate whether your water is:

• LSI < -0.5: Highly corrosive water (risk to equipment)
• LSI between -0.5 and 0.0: Slightly corrosive water
• LSI between 0.0 and +0.5: Balanced water (ideal)
• LSI > +0.5: Scale-forming water (risk of deposits)

Why Is This Important?

Monitoring and adjusting your water balance based on the Langelier Index can extend the life of your pool, reduce chemical use, and ensure a more comfortable and safe swimming experience. This calculator is part of our commitment to smarter water management — because Water Matters.