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| | | | LIMESCALE DEPOSITION The deposits formed by deposition from hard water supplies can be extremely detrimental to the performance of water systems. Limescale can cause blockages in pipework, efficiency losses and lead to the premature failure of components with a corresponding increase in maintenance costs. A sound understanding of the process of limescale deposition is important for anyone concerned with ensuring efficient and trouble free operation of water systems. All fresh water is derived from rainfall collected in rivers or as ground water. Water is one of the best solvents known which means that rain, falling on areas with predominantly chalk or limestone rock, percolates through the soil and underlying rocks slowly dissolving them. By the time that the water is pumped from bore-holes, rivers or reservoirs into the domestic supply system, it contains dissolved minerals known as hardness salts. These minerals may be beneficial to health, calcium for example, but may be deposited in the water systems in the form of scale with undesirable results. The mineral deposits that are collectively known as limescale, primarily consist of calcium and magnesium carbonates. Carbonates, which are generally insoluble, are deposited by heating water containing soluble bicarbonate salts. Bicarbonates are thermally unstable and break down to form carbonates, and thus scale, on heating. The main chemical reaction for scale formation is:
Factors affecting scale deposition
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