Hardness of water- this is a combination of chemical and physical properties of water associated with the content of dissolved salts of alkaline earth metals in it, mainly calcium and magnesium (the so-called "hardness salts").

Hardness salts have different properties. So, when water is heated, some of them precipitate in the form of scale, and some do not. On this basis, they began to separate.

The salts that precipitate out are called salts of temporary (or removable) hardness, and salts that do not precipitate when water is heated, salts of constant hardness.

Sulfates, chlorides and nitrates of magnesium and calcium, dissolved in water, form constant (or non-carbonate) hardness. They precipitate only when the water is completely evaporated.

Temporary stiffness characterized by the presence in water along with Ca2+, Mg2+ and Fe2+ cations of hydrocarbonate or bicarbonate anions (HCO3-).

When water is boiled, bicarbonates decompose, forming very poorly soluble calcium carbonate, carbon dioxide and water:

Ca2+ + 2HCO3- = CaCO3↓ + H2O + CO2

General hardness consists of permanent and temporary.

This table lists the main metal cations that cause hardness and the main anions with which they are associated.

In practice, strontium, iron, and manganese have such a small effect on stiffness that they are usually neglected. Aluminum (Al3+) and ferric iron (Fe3+) also contribute to hardness, but at the pH levels found in natural waters, their solubility, and thus "contribution" to hardness, is negligible. Similarly, the insignificant effect of barium (Ba2+) is not taken into account.

Water hardness - origin

Ions of calcium (Ca 2+) and magnesium (Mg 2+), as well as other alkaline earth metals that cause hardness, are present in all mineralized waters. Them source are natural deposits of limestone, gypsum and dolomite. Calcium and magnesium ions enter the water as a result of the interaction of dissolved carbon dioxide with minerals and other processes of dissolution and chemical weathering of rocks. Microbiological processes occurring in soils in the catchment area, in bottom sediments, as well as wastewater from various enterprises can also serve as a source of these ions.

Usually, in low-mineralized waters, hardness due to calcium ions prevails (up to 70%-80%) (although in some rare cases magnesium hardness can reach 50-60%). With an increase in the degree of mineralization of water, the content of calcium ions (Ca2+) drops rapidly and rarely exceeds 1 g/l. The content of magnesium ions (Mg2+) in highly mineralized waters can reach several grams, and in salt lakes - tens of grams per liter of water.

In general, surface water hardness is generally less than groundwater hardness. The hardness of surface waters is subject to noticeable seasonal fluctuations, usually reaching its highest value at the end of winter and the lowest during the flood period, when it is abundantly diluted with soft rain and melt water. Sea and ocean water have very high hardness (tens and hundreds of meq/dm3).

Water hardness - units of measurement

On January 1, 2014, Russia introduced the interstate standard GOST 31865-2012 “Water. Unit of hardness. According to the new GOST, stiffness is expressed in degrees of hardness (°F).

1 °F corresponds to the concentration of the alkaline earth element, numerically equal to 1/2 of its millimole per liter (1 ° W \u003d 1 mg-eq / l). In different countries, various non-systemic units were used (sometimes still used) - degrees of hardness.

Other units of measurement of water hardness are accepted abroad, the ratio of these units is presented in the table:

1 ° W \u003d 20.04 mg Ca 2 + or 12.15 Mg 2 + in 1 dm 3 of water;
1°DH = 10 mg CaO in 1 dm 3 of water;
1°Clark = 10 mg CaCO 3 in 0.7 dm 3 water;
1°F = 10 mg CaCO 3 in 1 dm 3 water;
1 ppm \u003d 1 mg CaCO 3 in 1 dm 3 of water.

The numerical values ​​of hardness measured in mg-eq/l, mol/m 3 , and °F, despite the differences in designation, are equal to each other.

By the value of the total hardness, natural waters are divided into groups:

• very soft water (0–1.5 meq/l)
• soft water (1.5–4 mg-eq/l)
• water of medium hardness (4–8 mg-eq/l)
• hard water (8–12 meq/l)
• very hard water (more than 12 meq/l).

Russian regulatory documents (SanPiN 2.1.4.1074-01 and GN 2.1.5.1315-03) for drinking water regulate:
calcium - the standard is not established; magnesium - no more than 50 mg / l; hardness - no more than 7 ° W.

Water hardness is remembered primarily with scale and a water softener - a device that must cope with hard water and prevent the formation of scale.

In more detail about water hardness, we will talk about water hardness in terms of chemistry, types of water hardness, units of water hardness (including in different countries). Consider where water hardness comes from and how hardness affects water quality.

First, a little about terms. The article often mentions the words "cations" and "anions". Cations and anions are positively and negatively charged ions. And he(ancient Greek ἰόν - going) - an electrically charged particle formed as a result of the loss or addition of one or more electrons. Accordingly, if the loss is, then the charge of the particle is positive. If attachment, then the charge of the particle is negative (since the electron has a uniquely negative charge).

Water hardness in terms of chemistry

The concept of water hardness is usually associated with calcium cations (Ca 2+) and, to a lesser extent, magnesium (Mg 2+). In fact, all divalent cations affect hardness to some extent. They interact with anions, forming compounds (hardness salts) capable of precipitating. Univalent cations (for example, sodium Na +) do not have this property.

This table lists the main metal cations that cause hardness and the main anions with which they combine.

In practice, strontium, iron and manganese have such little influence that they are generally neglected. Aluminum (Al 3+) and ferric iron (Fe 3+) also affect hardness, but at the pH levels found in natural waters, their solubility and thus "contribution" to hardness is negligible. small. Similarly, the insignificant effect of barium (Ba 2+) is not taken into account.

Varieties of water hardness.

There are the following types of water hardness:

General hardness. It is determined by the total concentration of calcium and magnesium ions. It is the sum of carbonate (temporary) and non-carbonate (permanent) hardness.

Carbonate hardness. It is determined by the presence of bicarbonates and carbonates (at pH> 8.3) of calcium and magnesium in water. This type of hardness is almost completely eliminated when water is boiled and is therefore called temporary hardness. When water is heated, bicarbonates decompose with the formation of carbonic acid and precipitation of calcium carbonate and magnesium hydroxide.

Non-carbonate hardness. It is caused by the presence of calcium and magnesium salts of strong acids (sulphuric, nitric, hydrochloric) and is not eliminated by boiling (constant hardness).

Units of measure for water hardness.

In world practice, several units of measurement of stiffness are used, all of them in a certain way correlate with each other. In Russia, the Gosstandart establishes a mole per cubic meter (mol / m 3) as a unit of water hardness. In Ukraine, both mol / m 3 and mg-eq / l (milligram equivalent per liter) are used. Numerically, these values ​​coincide. By the way, l and dm 3 are the same thing, a liter and a cubic decimeter.

In addition, hardness units such as German degrees (d o , dH), French degrees (f o), American degrees, ppm CaCO 3 are widely used in various countries.

The ratio of these stiffness units is presented in the following table:

Note:

1. One German degree corresponds to 10 mg/dm 3 CaO or 17.86 mg/dm 3 CaCO 3 in water.
2. One French degree corresponds to 10 mg / dm 3 CaCO 3 in water.
3. One American degree corresponds to 1 mg / dm 3 CaCO 3 in water.

In order not to bother with manual conversions, you can create a plate for converting hardness units. Which, by the way, you can download from the link Water hardness unit conversion table.

Where does water hardness come from?

Ions of calcium (Ca 2+) and magnesium (Mg 2+), as well as other alkaline earth metals that cause hardness, are present in all mineralized waters. Them source are natural deposits of limestone, gypsum and dolomite. Calcium and magnesium ions enter the water as a result of the interaction of dissolved carbon dioxide with minerals and other processes of dissolution and chemical weathering of rocks. Microbiological processes occurring in soils in the catchment area, in bottom sediments, as well as wastewater from various enterprises can also serve as a source of these ions.

Water hardness varies widely and there are many types of water classifications according to the degree of its hardness. The table below shows four examples of classification. Two classifications from Russian sources - from the reference book "Hydrochemical indicators of the state of the environment" and the textbook for universities "Water treatment". And two are from foreign countries: the stiffness standards of the German Institute for Standardization (DIN 19643) and the classification adopted by the US Environmental Protection Agency (USEPA) in 1986.

The table clearly illustrates a much more "hard" approach to the problem of stiffness abroad. And not without reason, as discussed below.

Usually, in low-mineralized waters, hardness due to calcium ions prevails (up to 70%-80%) (although in some rare cases magnesium hardness can reach 50-60%). With an increase in the degree of mineralization of water, the content of calcium ions (Ca 2+) drops rapidly and rarely exceeds 1 g/l. The content of magnesium ions (Mg 2+) in highly mineralized waters can reach several grams, and in salt lakes - tens of grams per liter of water.

In general, surface water hardness is generally less than groundwater hardness. The hardness of surface waters is subject to noticeable seasonal fluctuations, usually reaching its highest value at the end of winter and the lowest during the flood period, when it is abundantly diluted with soft rain and melt water. Sea and ocean water have very high hardness (tens and hundreds of meq/dm3).

How hardness affects water quality

From the point of view of drinking water use, its acceptability in terms of hardness can vary significantly depending on local conditions. The taste threshold for the calcium ion lies (in terms of mg-equivalent) in the range of 2-6 meq/l, depending on the corresponding anion, and the taste threshold for magnesium is even lower. In some cases, water with hardness above 10 meq/l is acceptable to consumers. High hardness worsens the organoleptic properties of water, giving it a bitter taste. and having a negative effect on the digestive organs.

World Health Organization does not offer any recommended hardness value for indications of health effects. The WHO materials state that although a number of studies have found a statistically inverse relationship between drinking water hardness and cardiovascular disease, the available data not enough to infer the causal nature of this relationship. The same way, not clearly proven that soft water has a negative effect on the balance of minerals in the human body.

However, depending on the pH and alkalinity, water with a hardness above 4 mEq/L can cause the deposition of slag and scale (calcium carbonate) in the water distribution system, especially when heated. That is why the norms of the Boiler Supervision introduce very strict requirements for the hardness of the water used to feed the boilers (0.05-0.1 mg-eq / l).

In addition, when hardness salts interact with detergents (soap, washing powders, shampoos), “soap slags” are formed in the form of foam. This leads not only to a significant waste of detergents. After drying, such foam remains in the form of a plaque on plumbing, underwear, human skin, and hair (an unpleasant feeling of “hard” hair is well known to many). The main negative impact of these toxins on a person is that they destroy the natural fatty film, which is always covered with normal skin and clog its pores.

A sign of such a negative impact is the characteristic "creak" of cleanly washed skin or hair. It turns out that the irritating “soapy” feeling that some people experience after using soft water is a sign that the protective fatty film on the skin is safe and sound. She is the one who slides. Otherwise, you have to spend money on lotions, softening and moisturizing creams and other tricks to restore the skin protection that nature has already provided us with.

At the same time, it is necessary to mention the other side of the coin. Soft water with a hardness of less than 2 meq/l has a low buffering capacity (alkalinity) and may, depending on the pH level and a number of other factors, have an increased corrosive effect on water pipes. Therefore, in a number of applications (especially in heat engineering), it is sometimes necessary to carry out special water treatment in order to achieve an optimal ratio between water hardness and its corrosiveness.

Here we learned more about the hardness of water. It remains to decide how to fight 🙂

Man is 70-80% water, which is the main solvent. With the help of it, oxygen, enzymes, hormones, salts are transported in the body. In this regard, the chemical composition of water becomes especially important: the more impurities it contains, the worse it dissolves useful substances.

Absolutely pure water is not found in nature. In contact with other macro- and microelements, it is enriched with various minerals, in particular, calcium and magnesium salts. It is their content that determines such a property as hardness: the more calcium and magnesium salts in the water, the harder it is.

In our country, water hardness is expressed in milligram equivalents per liter (mg-eq / l). Very soft water - up to 1.5 mg-eq / l, soft - from 1.5 to 4 mg-eq / l, water of medium hardness - from 4 to 8 mg-eq / l, hard - from 8 to 12 mg- eq/l and very hard - more than 12 mg-eq/l. The permissible limit of water hardness for centralized water supply is 7 mg-eq / l.

It has been proven that hard water has a negative effect on the body. When interacting with soap, “soap slags” are formed that are not washed off the skin, destroy the natural fatty film that protects against aging and adverse climatic factors, clog pores, form a microscopic crust on the hair, thereby causing a rash, itching, dryness, dandruff, peeling . The skin not only ages prematurely, but also becomes sensitive to irritation and prone to allergic reactions.

High hardness worsens the organoleptic properties of drinking water, giving it a bitter taste and having a negative effect on the digestive organs. Calcium and magnesium salts, combining with animal proteins that we get from food, settle on the walls of the esophagus, stomach, intestines, complicate their peristalsis (contraction), cause dysbacteriosis, disrupt enzymes and ultimately poison the body. The constant use of water with increased hardness leads to a decrease in gastric motility and the accumulation of salts in the body.

From water overflowing with calcium and magnesium ions, the cardiovascular system suffers excessively. Prolonged use of hard water is fraught with the occurrence of diseases of the joints (arthritis, polyarthritis), the formation of stones in the kidneys and biliary tract.

In addition to the fact that hard water negatively affects health, it also brings a lot of trouble in everyday life. It is undesirable for washing dishes and laundry - the dishes grow dull, and the fabrics wear out quickly. Huge damage is done to household appliances: boilers, washing machines and dishwashers, electric kettles and coffee makers. Calcium and magnesium salts, deposited on the heating elements, form hard lime deposits (scale) and pretty soon put the equipment out of action.

Traces of hard water are visible to the naked eye: a white coating appears on pipes, plumbing, in the heating system, household appliances, the consumption of detergents increases, soap “curls” during washing and washing, foamy slags form on the skin and surfaces.

Drinking water in some areas of the Republic of Mari El is characterized by a natural high content of hardness. Non-standard samples in terms of general hardness are detected by sanitary doctors as part of social and hygienic monitoring, in the course of control and surveillance activities and consideration of citizens' appeals.

Relevant resource-supplying organizations should carry out water purification before supplying to the population.

Complaints about the inadequate quality of drinking water can be addressed to the Office of Rospotrebnadzor in the Republic of Mari El.

Ordinary water consists not only of hydrogen and oxygen atoms, it also contains a large number of various impurities. It is the presence of impurities that determines the hardness of water, and the units of measurement (°F - degree of hardness) shows how much this indicator exceeds the permissible limits.

Water hardness is required to be determined not only by engineers who are engaged in laying communications, but also by ordinary people in everyday life. If we use an electric kettle or a washing machine with a water heating function, then all this can fail if this figure is too high. You are unlikely to be able to even dissolve soap well in such water.

How to determine the level of hardness of tap water, as well as methods for dealing with a high content of impurities will be described in detail in this article.

Hard and soft water - what's the difference?

The amount of salt in water is affected by the presence of calcium and magnesium elements dissolved in it. This indicator can also be significantly increased by the presence of iron hydrate, the content of which in artesian waters is sometimes excessive.

In the case when such impurities contain a small amount, it is called “soft”. This indicator is usually divided into 3 categories:

• Soft.
• Average.
• Rigid.

soft i is a rain or distilled liquid. There are practically no mineral impurities in such water.

In most cases, it can also be obtained as a result of prolonged boiling or the addition of special chemicals.

Medium- occurs most often in plumbing systems, as well as in spring and artesian water.

Rigid- this category includes sea, ocean, as well as water flowing from rock layers rich in mineral deposits. A large amount of salts can be dissolved in it. If taken as a percentage, then salinity can reach up to 33% of the total volume.

Consider the types of rigidity

This indicator is usually divided into the following categories.

• Constant - is a constant indicator, which depends on the content of sulfates and chlorides.
• Temporary - due to the content of calcium and magnesium bicarbonates. This type of hardness got its name for the ability to be almost completely neutralized as a result of boiling.
• The total stiffness is obtained by adding the indicators of constant and temporary.

In order to accurately determine this indicator, you need to know what units of measurement this can be done.

Rigidity units

For the correct calculation of the level of hardness, it is necessary to determine the concentration of calcium and magnesium cations. Currently, this indicator is defined in the following units of measurement:

• Mole/m3 (mol per cubic meter) - used in Russia until 2014.
• °Ж (degree of hardness) - this unit of measurement has been used in Russia since 2014.
• dH (German degree) - the unit of measurement used in European countries.
• fo (French degree) - also used in European countries.
• ppm CaCO3 (US degree) is the unit used in North American states.

It should be noted that in our country the expression of the total hardness mol / m3 has been used only since 1952. Until that time, calculations were carried out in degrees, which were equal to the modern German degree.

Since 2014, the international standard for calculating hardness has been in force in Russia, which is expressed in degrees (°F). One degree is equal to 1/2 millimoles per liter of liquid, so it is not difficult to calculate the level of concentration of a substance in a liquid.

Causes of water hardness

During the water cycle in nature, the liquid turns into vapor and rises to the upper atmosphere. After condensation, it precipitates in the form of precipitation and does not contain impurities that affect hardness, but passing through the layer of the earth's crust, the liquid dissolves various rocks that contain potassium and magnesium. Saturated with these elements, water increases its hardness. In the sea, it is always hard due to the high concentration of sodium chloride.

If it is necessary to reduce the concentration of potassium and magnesium ions, various methods can be applied to reduce the amount of salt impurities.

Methods for eliminating stiffness

To combat excessive salt content, the following methods are used:

Any of the proposed methods of water softening allows you to cope with a high level of this indicator, but the chemical method is usually not used to clean drinking water from salts.

How hardness affects water quality

The hardness of drinking water affects, first of all, its taste. The taste threshold of calcium ions in drinking water is 2-6 mg-eq/l. The taste threshold for magnesium ions is much lower, so the most pleasant drinking water is considered to be the one in which this indicator is from 1.6 to 3 mg-eq / l.

In some cases, water with a hardness of up to 10 mg-eq/l can be used as drinking water, but its long-term use can adversely affect human health. Too hard water is undesirable for use in liquid heating devices. Electric kettles, boilers, washing machines and dishwashers necessarily have a heating element in their design, which “acquires” deposits in the shortest possible time, and the process of heating the liquid is less efficient.

Long-term operation of an electric heater with a significant layer of scale leads to overheating of the element and its failure. Fortunately, for descaling, it is enough to dissolve 2 sachets of citric acid in 1 liter of water and boil a kettle or any other water heater well. After that, thoroughly rinse the device and use it further for its intended purpose.

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The high salt content of the water also negatively affects the washing process. Dissolving detergent in water rich in potassium and magnesium ions leads to excessive foam formation. Foam contributes to the formation of plaque on the elements of the washing machine, which can also adversely affect the performance of some components of this household appliance.

Human health implications

With prolonged use of hard water in the human body, serious deviations from the norm are observed, which are primarily manifested in the work of the following organs:

1. Gastrointestinal tract (GIT)- when the salts that make up hard water are combined with animal fats, fatty acid salts are formed, which envelop the walls of the stomach and intestines, preventing normal fermentation and significantly inhibit peristalsis. As a result, harmful substances and toxins accumulate in the body, and dysbacteriosis develops.
2. Joint work- some types of salts entering the human body form inorganic substances that eventually displace the synovial fluid from the joints. As a result of this replacement, the joints become covered with crystals, which cause severe pain when moving. Long-term use of hard water can lead to arthritis and polyarthritis.
3. The cardiovascular system- with a significant increase in the hardness of drinking water, the work of the heart worsens, up to the manifestation of severe arrhythmia.
4. Condition of the skin Hard water leads to premature aging of the skin. Negative effects are observed both when taking liquids inside, and when washing dishes. When dishwashing detergent comes into contact with hard water, a film is formed, which, when deposited on the skin, has a negative effect on the upper layers of the epidermis for a long time.
5. The formation of kidney stones- this statement is a myth that has been debunked thanks to the work of scientists. The process of stone formation does not depend on the quality of drinking water. Kidney stones are formed mainly due to a lack of calcium in the body. As a result of a deficiency of this element, it is washed out of the bones and deposited in the urinary system.

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All of these ailments and disease states can be avoided by using multi-stage water filtration. The use of such devices will not cost too much, but the treatment of various pathologies can cost significant amounts of money.

Methods for determining water hardness

To avoid the negative impact on the health of hard water, as well as to extend the life of heating devices, it is necessary to determine the approximate amount of potassium and magnesium salts dissolved in the liquid. Making it taste is quite problematic, because changes can only be detected in this way if a certain value is exceeded.

To determine at home the high content of potassium, magnesium and sodium salts, you can use the following methods:

• Try to dissolve soap in water, if foam does not form, then the water is very hard and should not be used.
• If a large amount of scale forms in the kettle and other appliances within a short period of time, then the water definitely exceeds the safe values ​​\u200b\u200bof this value.
• With the help of indicator strips, you can more accurately determine the amount of salts in the liquid, but this method will require small financial costs. To conduct the experiment, it is enough to lower the indicator strip into water for a few seconds, and after a minute compare its color with the table in the instructions.

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Conclusion

It is very important to know what hardness the water is used for drinking, as well as in heating boilers and other water heaters. It is not always necessary to use precise units of measurement for doing calculations at home.

In the chemical industry and other high-tech industries, on the contrary, you will need to know the amount of salts dissolved in water up to a milligram, so you can use any units of this indicator proposed in this article to determine and, if necessary, reduce the amount of salts in water.

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Entries

The degree of hardness of water is determined by the presence of ions in water calcium (Ca 2+), magnesium (Mg 2+), strontium (Sr 2+), barium (Ba 2+), iron (Fe 2+), manganese (Mn 2+). Moreover, the content of calcium and magnesium ions significantly exceed the concentrations of the other listed ions combined. Therefore, in Russia it is customary to determine the value of hardness as the sum of calcium and magnesium ions contained in water, expressed in milligram equivalents per liter (mg-eq / l). One meq/l corresponds to the content of 20.04 mg Ca 2+ or 12.16 mg Mg 2+ per liter of water.

There are carbonate (temporary, eliminated by boiling) and non-carbonate (permanent) hardness. Carbonate hardness is due to the presence of calcium and magnesium bicarbonates in water, non-carbonate hardness is due to the presence of sulfates, chlorides, silicates, nitrates and phosphates of these metals.

Temporary hardness is called because when boiled, calcium and magnesium bicarbonates decompose and precipitate in the form of carbonates. The chemical reaction of this process is as follows:

Ca(HCO 3) 2 - t o C → CaCO 3↓ + H 2 O + CO 2
Mg(HCO 3) 2 - t o C → CaCO 3↓ + H 2 O + CO 2

The resulting precipitate forms a plaque (so-called scale) on the walls of the dishes in which water is boiled. After boiling and precipitation of hydrocarbons, the water becomes softer.

Constant hardness is due to the presence in water of stable chemical compounds of sulfates, chlorides, silicates and some other salts of calcium and magnesium, which do not precipitate and are not removed when boiled. The sum of the temporary and permanent hardness gives the total hardness of the water.

General water hardness, standards

The world practice of quality control of water consumed for drinking (World Health Organization (WHO) standards, European Union (EU) standards, ISO standards, as well as US standards) do not standardize the hardness of drinking water - only separately the content of calcium and magnesium ions in water. According to Russian standards (), hardness should not exceed 7 mg-eq / l. What happens when this value is exceeded? It turns out that when water hardness is above 7 mg-eq/l, the rate of overgrowing of pipes with lime deposits increases significantly, which reduces their service life and increases operating costs. And at very low water hardness, it acquires strong corrosive properties. The active use of plastic and metal-plastic in recent years allows you to remove restrictions on the use of soft water.

General water hardness, classifications

Classifications of natural water according to the degree of hardness differ in different countries, and can also be subdivided depending on the purpose of using water.

The most general classification is as follows:

According to the American classification, drinking water is considered "soft" when the content of hardness salts is less than 2 mg-eq / l, normal - from 2 to 4 mg-eq / l, hard - from 4 to 6 mg-eq / l, and very hard - over 6 meq/l. It should be noted that such a classification is valid for water used for drinking purposes. The water in hot water systems and in contact with any heating elements must be softer for the normal functioning of the system. Here you can not do without installing, in particular -. At the same time, if the water comes from a private well, it is likely that a preliminary one will be required.

Detergent waste

In hard water from ordinary soap (in the presence of calcium ions), soap slags are formed - insoluble compounds that do not carry any useful functions. And until all the calcium hardness of the water is eliminated in this way, the formation of foam will not begin. There is a significant waste of detergents. After drying, such soap slags remain in the form of a plaque on plumbing, linen, human skin and hair (an unpleasant feeling of “hard” hair is well known to many).

Negative effect on tissues

Hard water is not suitable for washing and washing. Why? When soap or powder comes into contact with hard water, cations of hardness salts (Ca 2+, Mg 2+, Fe 2+) react with fatty acid anions that are part of the soap and form poorly soluble compounds, such as calcium stearate Ca (C 17 H 35 COO) 2. These deposits gradually clog the pores of the fabric and it ceases to allow air and moisture to pass through, the fibers become coarse and inelastic. The colors of the product fade and acquire a gray-yellow tint. “Lime soaps” that have settled on the fabric deprive it of its strength.

Skin irritation

When “hardness flakes” get on human skin, the natural fatty film is destroyed, which protects the skin from the adverse effects of the environment, and pores are clogged. A sign of such a negative impact is the characteristic “creak” of the skin or hair that appears after taking a shower. In fact, the “soapiness” that causes irritation in some people after using soft water is a sure sign that the protective fatty film on the skin is safe and sound. She is the one who slides. Or use hard water and compensate for the violation of the coating with lotions, softening and moisturizing creams and other tricks to restore the skin protection that nature has already provided us with.

Reduced equipment life

When water with a hardness of more than 4 mg-eq / l is heated against the background of high alkalinity and pH level, calcium carbonate is intensively precipitated in the form of scale (the pipes “overgrow”, a white coating forms on the heating elements). That is why the norms of the Kotlonadzor normalize the value of the hardness index of the water used to feed the boilers (0.05–0.1 mg-eq/l). In many industrial processes, hardness salts can react chemically to form unwanted intermediates.

Health impact

The World Health Organization regulates the values ​​of water hardness in terms of health effects. The materials of the organization say that although a number of statistical studies have revealed an inverse relationship between the hardness of drinking water and diseases of the cardiovascular system, the data obtained are still not enough to determine the causal relationship between these phenomena. Also, there is no evidence that soft water has a negative impact on the balance of trace elements in the human body. A number of studies suggest that human absorption of important minerals from water is extremely low, and he receives most of them from food.

Depending on local conditions, the acceptable hardness for drinking water use may vary somewhat. In some cases, water with hardness above 10 meq/l is acceptable to the consumer. The taste threshold for calcium ion (in terms of mg-equivalent) is in the range of 2-6 meq/l, depending on the corresponding anion, and the taste threshold for magnesium is even lower. So, water with high hardness can have a bitter taste. And long-term use of hard water (usually accompanied by high total mineralization) leads to problems in the gastrointestinal tract.

but on the other hand

It should also be noted that water with a hardness of less than 2 meq/l has low buffer properties (alkalinity) and, depending on the pH level and some other factors, may have an increased corrosive effect on the surfaces of pipes and heating equipment. Therefore, in some cases, especially when in boiler rooms, it is necessary to additionally carry out a special one, which makes it possible to achieve the optimal ratio between the corrosiveness of water and its hardness.