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Langelier Index

The Langelier Index is an approximate indicator of the degree of saturation of calcium carbonate in water. It is calculated PDF (58 KB) using the pH, alkalinity, calcium concentration, total dissolved solids, and water temperature of a water sample collected at the tap. If the;

  • Langelier Index is negative, then the water is under saturated with calcium carbonate and will tend to be corrosive in the distribution system
  • Langelier Index is positive, then the water is over saturated with calcium carbonate and will tend to deposit calcium carbonate forming scales in the distribution system
  • If Langelier Index is close to zero, then the water is just saturated with calcium carbonate and will neither be strongly corrosive or scale forming.

The Langelier Index is one of several tools used by water operators for stabilizing water to control both internal corrosion and the deposition of scale. Water supply operators can optimize their water supply systems and identify leakage potentials with the Langelier Index. Leakage is a common problem in Newfoundland and Labrador due to the acidic nature of provincial natural waters.

Experience has shown that Langelier Index in the range of -1 to +1 has a relatively low corrosion impact on metallic components of the distribution system. Langelier Index values outside this range may result in laundry stains or leaks.

A web based Langelier Index calculator can be found on the American Water Works Association (AWWA) webpage. opens new window

The Drinking Water Quality data shown on this page is now also available via the Newfoundland and Labrador Water Resources Portal. Using the Community Water Resources Reports feature a Community can be selected to generate reports that show all of the Drinking Water Quality data the Department has collected for that community.

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