SOFT-TEC® COMMERCIAL / INDUSTRIAL WATER CONDITIONER PROCESS LSI = pH - pHs pH is the measured water pH pHs is the pH at saturation in calcite or calcium carbonate and is defined as: pHs = (9.3 + A + B) – (C + D) Whereas A = (Log10 [TDS] – 1) / 10 B = -13.12 x Log10 (°C + 273) + 34.55 C = Log10 [Ca2+ as CaCO3] – 0.4 D = Log10 [alkalinity as CaCO3] Langelier Saturation Index The Langelier Saturation Index (LSI) is a formula that was devised by Professor Wilfred F. Langelier (1886-1981) in order to quantify the propensity of a given source water to forming scale or corroding plumbing systems (and thereby leaching metals from plumbing components and fixtures into drinking water etcetera). The formula is based on the concept of ‘’Water Balance’’ or ‘’Saturation’’ where the carbonic acid (H2CO3) and the calcium carbonate (CaCO3) present in the water are in a perfect state of equilibrium. The Soft-Tec® salt and chemical free scale control media requires the presence of ‘’available’’ or ‘’excess’’ calcium in order to produce and release the seed crystals into the treated water which then serve as nucleation sites for precipitating calcium further down the plumbing system. In order to calculate the LSI, it is necessary to know the alkalinity (mg/l as CaCO3), the calcium hardness (mg/l Ca2+ as CaCO3), the total dissolved solids (mg/l TDS), the actual pH and the temperature of the water (°C). LSI is defined as: As indicated above, the Soft-Tec® media requires available calcium to promote the formation of seed crystals. It can only do so reliably if it can induce the precipitation of calcium from a dissolved state into calcium carbonate crystal formations. Therefore, without proper pretreatment, the Soft-Tec® media should only be applied to treat water that has a neutral or positive LSI. Any method that would shift any of the parameters that are inputs into the LSI upwards (i.e. raising the pH, alkalinity or temperature etc.) would be acceptable methods. For the purposes of water treatment, however, the most common approaches are aeration and/ or pretreatment with a neutralizer like calcite or dolomite to bring the water into a balanced state. Indeed, when used with corrosive water without pretreatment, the Soft-Tec® media itself will suffer the corrosive effects of the water and the functional surface will be dissolved over time rendering the media ineffective. The formula above will return values > above and < below zero. The interpretation of the results are as follows: LSI INDICATION LSI < 0 Water is under saturated with respect to calcium carbonated LSI = 0 Water is considered to be neutral. Neither Scale Forming nor Scale Removal LSI > 0 Water is supersaturated with respect to calcium carbonate and Scale Forming may occur - 2.0 < - 0.5 Serious Corrosion but Non Scale Forming - .5 < - 0 Slightly corrosive but Non Scale Forming LSI = 0.0 Balanced but pitting corrosion possible 0.0 < 0.5 Slightly Scale Forming and possibly corrosive 0.5 < 2.0 Scale Forming but non corrosive
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