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Langelier Index
Introduction to Water Corrosivity
Water corrosivity is important for maintaining safe and high-quality drinking water because it affects pipes, plumbing, and water equipment. Corrosive water can dissolve metals like lead and copper from pipes, causing leaks, damage, and contamination. Understanding and controlling corrosivity helps prevent costly repairs and ensures balanced water for consumption.
The Langelier Saturation Index (LSI) is a common tool to assess water’s corrosive or scale-forming tendencies. It uses factors like pH, water temperature, total dissolved solids (TDS), total alkalinity, and calcium hardness. The LSI indicates if water will dissolve calcium carbonate (corrosive) or form scale by precipitating it.
A low or negative LSI means high corrosion potential; the water lacks calcium carbonate and may dissolve minerals from pipes. A high or positive LSI shows a tendency to form scale, which can clog pipes.
To calculate the LSI, compare the water’s pH with its calcium carbonate saturation. Using a calculator allows users to quickly determine the LSI and assess whether the water is likely to cause corrosion or scale. This is especially helpful for well water, which often requires special treatment to stay balanced.
When water is corrosive, treatment depends on the severity. Severe cases may require adjusting the pH, increasing alkalinity, or adding calcium hardness to restore balance. Moderate corrosion can often be managed by adjusting water temperature or applying corrosion inhibitors. By understanding the LSI, homeowners and water professionals can take action to protect plumbing systems, lower maintenance costs, and ensure safe, high-quality water.
Resources:
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- EPA: Lead and Copper Rule – Corrosion Control – See how the EPA regulates corrosion control in drinking water systems.
Langelier Index calculator (online calculator)
This calculator helps you determine the scaling potential of the water by using the Langelier Saturation Index
Give the values of your water analysis. All the fields with * are required.
Negative Index? Your Water Is Corrosive
A negative Langelier Index means your water is dissolving copper and metal from your pipes and fixtures. An acid neutralizer filter raises the pH and alkalinity to bring the index back toward balance.
Shop Acid Neutralizer Filters
Positive index (scale-forming)? See water softeners →
Please Note- SI Index is not a reliable means of evaluating corrosion potential, but it can be used as a guide.
