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Lime is not only present as rock in nature, but also in dissolved form, as calcium carbonate (CaCO3) and magnesium (Mg) in water. If the mineral content is high, we speak of hard water.
How does lime get into the water?
The percolating, acidic rainwater dissolves minerals from the soil on its way from the surface to the groundwater and transports them in dissolved form past the waterworks and into our households.
Lime is basically very poorly soluble in water. It is converted into a readily water-soluble form by reaction with carbonic acid, which is bound by means of precipitation from the air. The amount of dissolved lime is related to the carbonic acid content in the water. This balance is called the lime-carbonic acid ratio.
A change in this lime-carbonic acid equilibrium causes the lime to convert back to its non-water-soluble form.
Stress potential in pipelines exerts an attractive force on the minerals (lime) in the water, so that they bind and settle there. A lime layer (lime deposit) is formed, which is harmful to all water-bearing pipes and equipment and entails considerable costs.
Lime is not just lime
Lime directly from natural water sources contains an above-average volume of carbonic acid and is successively exposed to flow dynamics and air molecules, which stabilize the carbonic acid-lime balance.
Lime after water treatment is located in closed piping systems and is exposed to constant mechanical pressure. This disturbs the carbonic acid-lime balance, which is why calcification progresses aggressively.
Water hardness depends on the content of calcium, magnesium, stronium and barium ion compounds in water. It is formed when calcium and magnesium combine with carbon dioxide dissolved in water. These can form insoluble compounds - lime is formed. Typically, this appears as lime deposits on the faucets in the kitchen, all water-bearing household appliances, as well as in the bathroom.
The hardness of water, according to DIN 19640 the content of alkaline earth ions in the water: mainly magnesium (Mg hardness) and calcium (Ca hardness), but also barium (Ba hardness) and strontium ions (Sr hardness). A distinction is made between temporary or transient hardness and permanent or permanent hardness, which together give the total hardness. Since the hardness of water can vary considerably depending on the landscape and the season, so-called degrees of hardness have been introduced to characterize the water. 1°dH corresponds to 10 mg of calcium oxide (CaO) per liter of water or the equivalent amount of another alkaline earth oxide (7.14 mg MgO, 27.35 mg BaO, 18.48 mg SrO). Hard water is undesirable because soaps form insoluble salts with the calcium compounds and because scale is deposited in steam boilers.
When water is heated, limescale can build up in the drinking water installation and coat pipe walls, heating registers and heat exchangers, but also pumps and control valves. Pressure losses and narrowing of the line cross-sections up to complete blockage are possible. Unpleasant and often extremely expensive malfunctions in the drinking water installation and technical systems can be the result.
Hard water causes unsightly and stubborn evaporation residues on stainless steel and glass surfaces or tiles, which are often difficult to remove. Calcified cooking pots, kettles and coffee machines or clogged aerators and shower heads on fittings are well known.
Limescale deposits act like an insulator and thus lead to reduced heat transfer in the heating registers and heat exchangers. The consequence is rising maintenance and energy costs.
Under certain conditions, encrustations in the pipelines can promote the build-up of a biofilm, which drastically increases the hygiene risks. These biofilms provide ideal habitats for undesirable microorganisms and pathogens (e.g. legionella). Limescale deposits also make the necessary chemical or thermal disinfection of the drinking water installations more difficult. A thorough cleaning (removal of all lime deposits) should be carried out on older drinking water pipes be carried out - albeit at a cost. Limescale layers in boilers and heat exchangers lead to low temperatures. Lime drastically reduces heat transfer, with the result that legionella and bacteria grow faster and are protected (between layers of lime).
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