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Updated on: 06/12/2019

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Calcium or calcium is a vital element for the human body and occurs in nature only chemically bound as a component of minerals, e.g. in limestone, marble, chalk or gypsum. Since calcium compounds are water-soluble, they are rinsed out by natural weathering of calcium-containing rock and thus get into ground water and drinking water. The Drinking Water Ordinance does not specify a limit value for calcium, since the mineral is an important building block for the formation of bones and teeth as well as for many metabolic functions. The German Nutrition Society recommends a daily dose of calcium of 1000 mg for adults.

In combination with magnesium, calcium determines the water hardness. Hard water forms strong limescale deposits, which can cause more serious problems in pipelines. The lime coating narrows the passage of water pipes and calcifies household appliances and boilers. Limescale formation also has a negative effect on the taste of the water. In contrast, soft water is more suitable for cooking and for hot drinks such as tea or coffee.


Magnesium occurs as an alkaline earth metal in nature exclusively chemically bound as a component of numerous minerals such as carbonite, silicate and dolomite. In agriculture, magnesium is an important component of fertilizers and animal feeds. Together with calcium, it is responsible for water hardness in water, but the proportion is only 15-30 %.

It is essential for the human organism, especially for muscle and nerve cells, and is ingested daily through food (e.g. whole grain and dairy products) and drinking water. Magnesium deficiency leads to disturbed metabolic functions, which can result in nervousness, lack of concentration, fatigue, weakness and muscle cramps.

Mainly due to natural weathering and leaching of mineral-bearing rock, magnesium reaches the ground and drinking water. One litre of tap water contains approx. 10 mg magnesium. There is no limit value for magnesium in the Drinking Water Ordinance. On the other hand, data on concentration are mandatory for mineral waters.

Just like calcium, Magesium causes calcium deposits and adversely affects the taste of drinking water. In the long term, it can lead to problems with the passage of water and to failures due to calcification, especially in domestic installations.


Potassium is a frequently occurring element contained in numerous minerals as a potassium compound. About 95% of the potassium used is used as potassium nitrate in fertilizer production, but also in industry. Potassium in its pure form is not soluble in water, but only as a potassium compound. From these, the element can detach itself through weathering processes and enter the groundwater.

Potassium is also an essential element for the human body and occurs mainly in the brain, red blood cells and muscle tissue. It controls processes such as blood pressure, the nervous system or muscle contractions. It is consumed with the daily food (e.g. bananas) or through drinking water. With the help of its counterpart sodium, potassium regulates the osmotic balance in the cells and thus also the body's fluid balance. As electrolytes, sodium and potassium are especially important after sweating sport, otherwise cramps or exhaustion can occur.

Potassium compounds are used in agriculture as fertilizers and thus also get into ground water and drinking water. No limit value for potassium was included in the Drinking Water Ordinance 2017. Some potassium compounds such as potassium chloride, potassium carbonate or potassium permanganate are toxic, but potassium permanganate is used in water treatment to remove iron and manganese.


Sodium, is a frequently occurring, highly reactive light metal that is always bound in nature. The best known sodium compound is sodium chloride, our common salt. Sodium salts are almost all soluble in water and can be found in the oceans, in rocks and in sedimentary layers, so-called brines. The salt content of the seas is on average 35 grams per litre, in the Dead Sea it is about 280 grams.

Sodium is a natural component of water and reaches groundwater from soils, rock layers and salt deposits. 100 millilitres of drinking water contain about 4 mg sodium. Sodium is vital for the human body and, along with calcium and potassium, is one of the body's quantitative elements. Sodium influences the water balance, the acid-base balance, the electrical voltage in cells and the transmission of stimuli to the nerves. According to the German Nutrition Society (Deutscher Gesellschaft für Ernährung), adults should
not to consume more than 1.5 g per day. But through industrially processed food and fast food, most people consume unnecessarily much salt. Sodium excess can lead to high blood pressure. Babies and toddlers should also drink low-sodium water. Mineral water is considered to be low in sodium if it has a sodium concentration of less than 200 mg/l. At approx. 50 mg/l, tap water is significantly lower. A contamination by sodium-containing drinking water is therefore rather unlikely.


Iron is a common metal and a major component of our earth's core. Iron tends to corrode in humid environments, it rust. Biologically, it is of essential importance for living organisms, as it is primarily responsible for the transport of oxygen in red blood cells. The daily requirement for humans is about 10-15 mg per day. Iron deficiency has a harmful effect on health.

Iron is released and enters the groundwater and drinking water, but in concentrations far below critical health levels. Even old iron pipes or galvanized metal pipes or fittings can be used to introduce iron into drinking water. Homeowners of older buildings are themselves responsible for compliance with the limit values. From an iron concentration of more than 0.5mg/l, brown discolorations, deposits and a metallic taste of the water occur. However, a health hazard only exists above an iron content of 200 mg/l.


Sulphates are salts of sulphuric acid that occur naturally as mineral compounds. Most sulphates are readily soluble in water and occur in various concentrations in groundwater. According to the Drinking Water Ordinance, the limit value for sulphate is 250 milligrams per litre. Increased sulphate content in water causes damage to pipes and fittings.

Sulphate is vital for the human body, as it is involved in the formation of proteins that influence the growth and stability of cartilage, skin, hair and nails. In addition, sulphate has a digestive effect as it stimulates the flow of bile. Excessive concentrations in drinking water, on the other hand, have a laxative effect and can cause osmotic diarrhea, especially in infants. The taste of tap water becomes bitter with too much sulphate.