Langelier Saturation Index Calculator

Formula

To calculate the Langelier Saturation Index (\(LSI\)):

\[ LSI = pH - pHs \]

Where:

\(LSI\) is the Langelier Saturation Index
\(pH\) is the actual pH of the water
\(pHs\) is the saturation pH of the water

What is the Langelier Saturation Index?

The Langelier Saturation Index (LSI) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. LSI is used in the water treatment process to manage the scaling and corrosion tendencies of water. A positive LSI indicates the water is supersaturated and has a tendency to form scale, while a negative LSI indicates the water is undersaturated and has a tendency to dissolve existing scale.

Example Calculation 1

Let's assume the following values:

Actual pH of the Water (\(pH\)) = 7.5
Saturation pH of the Water (\(pHs\)) = 7.2

Using the formula:

\[ LSI = 7.5 - 7.2 = 0.3 \]

The LSI is 0.3, indicating a tendency to precipitate scale.

Example Calculation 2

Let's assume the following values:

Actual pH of the Water (\(pH\)) = 6.8
Saturation pH of the Water (\(pHs\)) = 7.0

Using the formula:

\[ LSI = 6.8 - 7.0 = -0.2 \]

The LSI is -0.2, indicating a tendency to dissolve scale.