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Langelier Saturation Index Calculator

This converter requires the use of Javascript enabled and capable browsers. This script determines water balance calculations. Once you have measured the various parameters below, you can use this convenient Langelier Saturation Index calculator to determine whether your water is corrosive, scale forming or nicely balanced. If the water is corrosive, the water will try to saturate itself by dissolving the surface composition structure of your pool. If it is scale forming it will try to correct its over saturation by precipitating the hard water salts causing cloudy water and eventually deposit scale on pool components.

Saturation Index = pH + calchd + totak + tmpc - 12.1

In the above formula:
calchd is the Calcium Hardness factor. Optimum range 75 to 150 mg/liter.
totak is the Total Alkalinity factor. Optimum range 100 to 150 mg/liter.
tmpc is the Temperature in Degrees Centigrade. Suggested water temperature is between 27 and 29.5 Degrees C in commercial pools.
pH. Optimum range 7.2 to 7.6.

If the result of this calculation is zero, the target goal, then the water is balanced. If the answer is less than 0, the water leans toward being corrosive. If it is greater than 0, then it is indicative of scale forming. An acceptable range is -0.5 to +0.5, with the optimum goal of 0 (zero). If the result is outside this range, adjustments should be made to the hardness, alkalinity and pH to bring it as close to zero as possible and ideally within the optimum ranges shown above. Be aware however, that while the water may be balanced from a corrosion and scaling point of view it does not necessarily mean that it is ideal for chemical efficiency and bather comfort.

Required Data Entry
Total Alkalinity
Calcium Hardness
Measured pH

Calculated Results
Langelier Saturation Index
Version 1.4.2

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