At first glance, such a concept as water hardness sounds strange - if we were talking about ice, then everything would be much clearer. But in fact, much attention is paid to this characteristic quite often, and in different areas since water affects human health. Below we will answer the question of exactly how and what methods should be used in order to determine the hardness of water.

In this article, you will learn:

How to determine water hardness using instruments

How to determine water hardness at home

What salts determine the hardness of water

Why is it necessary to determine the hardness of water

An indicator such as water hardness directly depends on how much calcium and magnesium salts it contains. Water hardness is an ambiguous concept, since it can be sulfate or carbonate, this can be determined in different ways.

At its core, water hardness is the positively charged calcium and magnesium ions that are dissolved in it. This indicator can be determined as follows: if its value is high, then when the container with water is heated, a raid from salts will appear on its walls.

A person is also susceptible to the appearance of a similar plaque, but it manifests itself in a completely different way: stones in the gallbladder, kidneys or liver. It is important to determine the hardness of water, since the possibility of further use of the liquid in a particular area depends on this value.

You should have questions about the hardness of the water at home or in the office in the event that scale appears on the kettle, the boiler does not work well, Washer washes poorly. In such situations, it will be useful to determine the value of this indicator, for example, by passing a sample for analysis to a laboratory.

How to determine the hardness of different types of water

How to determine the carbonate and non-carbonate hardness of water

Carbonate hardness is almost 100% of all cases, but in order to determine what it is, you need to use special methods.

What can be done to determine the carbonate hardness of water:

make a chemical test for hardness;

contact the laboratory;

buy a special test in the store that will determine the hardness of the water;

seek help from specialists.

How to determine temporary water hardness

The presence of temporary water hardness is characterized by the presence in its composition of positively charged ions of calcium, magnesium and iron, bicarbonate and hydrocarbonate anions (II). It can be defined as follows: when such water is heated, hydrocarbonates decompose, but a slightly soluble carbonate precipitate, water and carbon dioxide are formed.

How to determine the constant water hardness

In order to determine the constant hardness of water, it is necessary to determine the content of calcium and magnesium salts in it - sulfates, phosphates and chlorides, which completely dissolve in water and do not precipitate during boiling. Water can be purified from them using filters with ion exchange resin, reverse osmosis or electrodialysis. To determine the indicator of the total hardness of water, you need to add up the indicators of temporary and permanent hardness.

How to determine water hardness in a laboratory

How to determine water hardness using special devices

Water must have optimal indicator rigidity, since the complete absence of salts is harmful to the human body. If the water, for example, is low in carbonate salts, this leads to the appearance of cardiovascular diseases.

If we talk about the containers themselves, in which the water is heated, then soft water promotes corrosion. Therefore, after operation of equipment with soft water in heat power engineering, the surfaces are additionally treated with a solution containing substances that slow down this process.

Thus, water, from whatever source you take it, has some kind of hardness indicator, and ideally, if it has an average value, because both an excess of salts and their lack lead to certain consequences.

Determining the hardness of water in our time is not difficult - now you can purchase special devices to control this indicator both in the house and at work. The best option – TDS-3 device, in the market it can be found under various trade names.

You can use another device that allows you to determine the hardness of the water - electrolyzer. This is a fairly cheap device.

The electrolizer will not be able to determine the level of water hardness in numbers, but it will color the liquid in a certain color depending on how much salt it contains. After electrolysis, you will understand which impurities you are dealing with also by the color of the water.

You can make a similar device yourself, for this take:

stainless steel, size 50 x 50 cm;

bolts M6 x 150;

• transparent tube;

• Plastic container a volume of one and a half liters;

  filter for water purification;

  check valve for water.

The basis for the future device will be a sheet of stainless steel, ideally - AISI 316L, if it is imported, and 03X16H15M3, if it is domestic.

Now the stainless steel needs to be marked and cut into 16 identical squares, after which we cut off one corner of each of them, and drill a hole on the opposite corner, which will come in handy a little later. The principle of operation of the electrolyzer is the movement of electricity from a plate of one charge to a plate of opposite charge, as a result, water decomposes into oxygen and hydrogen.

In order to create a good current flow, the plates are connected in turn: first a positive charge, then a negative one, then a positive one, etc. The tube is used for insulation, a ring must be cut off from it, cutting which we get a strip 1 mm thick.

Washers are needed in order to assemble the plates: screw the washer onto the bolt, then the plate and three washers, then the plate again, and so on. Each charge should have eight plates. All this must be done carefully enough to avoid contact of the cuts of the plates with the electrodes.

The next step in creating a device for determining the quality of water is tightening the nuts and insulating the plates, after which we place the result in a plastic container of a suitable size.

In the places where the bolts touch the walls of the box, we drill two holes. It may happen that the bolts do not pass into the container, then cut them off and tighten with nuts for tightness. Now we drill a hole in the cover for the fittings. To create the tightness of the seam, we treat it with silicone sealant.

Before you are going to determine the water hardness with such a device, you need to check if it works well enough: connect the device to the power supply, fill up the bolts with water, cover with a lid, connect a tube to the fitting and lower the other end of the tube into water. If the current appears, then it can be seen.

Now the current must be gradually increased. Distilled water, due to its purity, conducts a current very poorly, therefore, to create an electrolyte, it is necessary to add alkali, for example, sodium hydroxide (present in "Mole" type pipe cleaners). The safety valve prevents excessive accumulation of gases. Congratulations, you have a hand-made device that will allow you to determine the hardness of your water!

How to determine water hardness using soap

This method was described by I. Sheremetyev. It is based on the difficulty of diluting laundry soap in hard water. Lather appears when the soap binds excess calcium and magnesium salts.

You can determine the hardness of water in this way: we take 1 g of laundry soap, grind it and gradually, carefully, avoiding the appearance of foam, dissolve it in a small amount of hot distilled water.

Pour the resulting solution into a cylindrical glass, now you need to add distilled water to it to a level of 6 cm, if the soap is 60%, or to a level of 7 cm, if the soap is 72% (this percentage is indicated on the bar of soap itself). For every centimeter of the available solution, there is an amount of soap that can bind hardness salts, they contain 1 ° dH per 1 liter. water. Now we take a liter jar and fill it halfway with the water whose hardness we want to determine. Then, with constant stirring, gradually pour the prepared solution into it. At first, only dark flakes will be visible, and then colored bubbles will appear. If a dense white foam is formed, this indicates that all hardness salts in the water under study are bound. Now we need to calculate how many centimeters we poured from the prepared solution - each centimeter tied in half a liter of water the amount of salts corresponding to 2 ° dH, that is, if 4 cm of soap solution had to be added to obtain foam, then the hardness of the water under study is 8 ° dH.

In the event that the solution has already ended, and there is still no foam, we are dealing with a water hardness exceeding 12 ° dH. Then, in order to determine the desired value, we repeat the experiment, but dilute the test water twice with distilled water. The result that we get as a result of the repeated analysis should be multiplied by two, this will be the desired indicator of water hardness.

Ordinary glasses, as a rule, have approximately the following parameters: volume - 200–250 ml, height –10 cm, lower diameter - 55 mm or more, upper diameter - 73 mm. Thus, its average diameter is approximately 63 mm. You can most accurately determine the hardness of water if you use a chemical cylindrical glass with a diameter of about 6 cm.Of course, you can use a conical glass, but then the error will be greater. It should be noted that one should not expect an absolute measurement accuracy from this method, but an accuracy of 1–2 ° dH is quite enough to determine the state of water. This error is largely due to the difference between the upper and lower diameters of the vessel in which the soap solution is located, and is also influenced by the quality of the soap, distilled water and your experience with this analysis.

This method is very simple and allows you to independently determine the hardness of water, so such a small error in determining this indicator should not force you to refuse to use it.

How else to determine water hardness at home

In fact, it is not difficult to determine the hardness of water. If you need to know the exact number, you can always take the sample for analysis to the laboratory. The most optimal way to determine water hardness is to conduct a test using the Trilon B reagent. It is also possible to get quick results using special equipment, the minimum cost of which is $ 10-15. This is a little money if you need to frequently monitor this indicator at home.

If you do not have this equipment, but you need to determine the hardness of water right now, you can use the following method. Just take a bar of soap and wash with it - if there is no foam and the skin is drying, and there is a deposit on the shower head or in the kettle, then the water is hard. If the opposite is true, then the water is soft or medium hard.

Actually exist some more ways to determine the stiffness indicator:

The most accessible method involves determining the quality of water by outward appearance and taste. Ideally, it is transparent, free of sediment and foreign odor.

To determine how clean the water is, it must be poured into a transparent, clean glass 20 cm long and placed on a sheet with text. If the text can be read through the water, then this indicator is normal.

The color of water can be determined in a similar way, only you need to pour 100 ml of water into a glass and put it on white paper. If there are organic impurities in the water, the liquid darkens.

The smell can be used to determine the purity of the liquid. Heat the water to 20 ° C, then to 60 ° C. If you notice an unpleasant putrid smell, it means that there are impurities of hydrogen sulfide in it.

Taste also allows certain qualities to be identified. To do this, pour water into a clean dish, boil a small amount of water for five minutes, then cool to 20 ° C – 25 ° C, now try it. A sweetish taste indicates the content of gypsum in it, bitter - magnesium salts, tart - iron salts. A putrid taste appears from the ingress of plant or animal organisms into the water. After filtering, you can determine the presence of solid impurities, but first, the water must be defended for some time.

Try dripping water onto a glass or mirror. After the liquid has evaporated, examine the surface: if it remains clean, the water is also clean. Stains are a clear sign of poor water quality. Take a closer look at the aquarium, if you have one, its inhabitants are usually very sensitive to water quality.

The above methods will not allow you to accurately determine the hardness and quality of water, so it is best to contact a specialist.

If you need to determine the hardness of water for a house, summer cottage or cottage, it is best to do an analysis, since the amount of magnesium and calcium in it can be any, depending on many factors.

You will spend money on analysis, but you will know exactly how effective the purchased filter will be.

Exists a large number of Russian companies developing water treatment systems. Relying only on yourself, choosing the right filter is difficult. Making a purification system at home by yourself, even if you read a little about it beforehand, will not be enough effective way cleaning.

It is safer to contact a filter installation company that provides a full range of services: specialist advice, analysis of water from a well or well, selection of suitable equipment, delivery and connection of the system. In addition, it is important that the company also provides filter service.

This is the company Biokit which offers a wide range of systems reverse osmosis, water filters and other equipment capable of returning tap water to its natural characteristics.

The specialists of our company are ready to help you:

connect the filtration system yourself;

understand the process of choosing water filters;

pick up replacement materials;

troubleshoot or solve problems with the involvement of installers;

find answers to your questions by telephone.

Trust Biokit water purification systems to keep your family healthy!

Hardness is a property of water due to the presence of soluble calcium and magnesium salts in it.

Hardness of water- this is one of the main criteria for water quality.

Hardness chemistry

Concept water hardness it is customary to associate with calcium cations (Ca 2+) and, to a lesser extent, magnesium (Mg 2+). In fact, all divalent cations affect hardness to one degree or another. They interact with anions to form compounds (hardness salts) that can precipitate. Monovalent cations (for example, sodium Na +) do not have this property.

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

In practice, strontium, iron and manganese have so little effect on hardness 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, accordingly, the "contribution" to hardness is negligible. Similarly, the insignificant influence of barium (Ba 2+) is not taken into account.

Types of stiffness.

Distinguish the following types rigidity.

Overall 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.

The table clearly illustrates a much more "rigid" approach to the problem of "their" rigidity. There are reasons for this, which are discussed below.

Usually, in low-mineralized waters, hardness due to calcium ions predominates (up to 70% -80%) (although in some rare cases, magnesium hardness can reach 50-60%). With an increase in the degree of water mineralization, the content of calcium ions (Ca 2+) decreases 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, the hardness of surface waters is usually less than the hardness of groundwater. Surface water hardness is subject to significant seasonal fluctuations, usually reaching the greatest value at the end of winter and the least during the flood period, when it is abundantly diluted with soft rain and melt water. Sea and ocean water have a very high hardness (tens and hundreds of meq / dm 3).

Effect of hardness on water quality.

From the point of view of the use of water for drinking needs, its acceptability in terms of the degree of hardness can vary significantly depending on local conditions. The taste threshold for calcium ion is (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 a hardness higher than 10 mg-eq / l is acceptable for consumers. High hardness impairs the organoleptic properties of water, imparting a bitter taste to it and having a negative effect on the digestive organs.

The World Health Organization does not offer any recommended severity value for health indications. The WHO materials say that although a number of studies have revealed a statistically inverse relationship between stiffness drinking water and cardiovascular diseases, the available data are not sufficient to conclude about the causal nature of this relationship. Likewise, it has not been unequivocally proven that soft water has a negative effect on the mineral balance in the human body.

At the same time, depending on pH and alkalinity, water with a hardness higher than 4 mEq / l can cause the deposition of slags and scale (calcium carbonate) in the distribution system, especially when heated. That is why the norms of Kotlonadzor introduce very stringent requirements for the value of water hardness used to power 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 significant cost overruns detergents... After drying, such foam remains in the form of a plaque on plumbing fixtures, linen, human skin, on the hair (the unpleasant feeling of "coarse" hair is well known to many). The main negative effect of these toxins on humans is that they destroy the natural fatty film that is always covered with normal skin and clog its pores. A sign of such a negative effect is the characteristic "squeak" of cleanly washed skin or hair. It turns out that the irritating feeling of "soapy" after using soft water, which causes some irritation, is a sign that the protective fatty film on the skin is intact and intact. It is she who slides. Otherwise, you have to spend money on lotions, softening and moisturizing creams and other tricks to restore the skin protection that Mother Nature already provided us with.

At the same time, it is necessary to mention the other side of the coin. Soft water with a hardness less than 2 mEq / l has a low buffer capacity (alkalinity) and can, 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 a special treatment of water in order to achieve an optimal balance between water hardness and its corrosiveness.

Industrial methods

Negative influence of hard water applies not only to household water heating devices, but also to the state of the body of people who use it. In this regard, in the water supply system, the most urgent problem is purification and. And it should be noted that this problem literally faces every homeowner, regardless of where he lives - in a city apartment or in a private house. And even those people who have installed autonomous water supply systems have problems with hard water.

Water becomes hard due to the high content of magnesium and calcium salts in its composition. Consequently, their number has a direct impact on the choice of treatment systems. The amount of hardness salts can be determined in a chemical laboratory, where water samples should be taken before deciding in favor of a particular installation. The unit of measurement for hard water is the milligram equivalent per liter of water. But the classification of stiffness in different countries happens in different ways. For example, in America it is classified as follows:

• soft - the content of magnesium and calcium is up to 2 mg-eq / liter;
• normal - within 2-4 meq / liter;
• hard - 4-6 meq / liter;
• very hard - more than 6 meq / liter.

And if a laboratory analysis shows a hardness level of more than 2 meq / liter, then this means that a softener must be installed.

But there are certain areas of human activity for which influence of hard water does not apply. This can be, for example, putting out a fire, watering vegetable gardens or green spaces in cities, cleaning streets. In these cases, installing softening filters is impractical and even economically unprofitable, since they are not practical. However, the impact of too hard water on people's lives is more than negative.

Along with those moments in which hard water has no effect, there are those in which water softening is of great importance. This mainly concerns its use for domestic needs - the operation of washing machines and dishwashers, water heating boilers and boilers, while taking a shower, while drinking it inside. In all these cases, in order to reduce the negative effect of too hard water, it is necessary to use special devices.

Using soft water will help you avoid many problems. And this is easy to explain, because:

Using less hard water not only reduces the negative impact, but also allows you to reduce the consumption of detergents by almost half.

The combination of hard water and detergents leads to the formation of "soap slags" that are very difficult to wash off. In addition, unpleasant stains appear in the bathroom, sink, and dishes.

"Soap slags" are very poorly washed off not only from household items and devices, but also from human skin. Moreover, the pores of the skin become clogged, which causes itching and irritation. In addition, the negative effect is manifested in the form of dry skin, in the appearance skin diseases and irritations. And as a result, you have to use protective cosmetics.

During boiling of hard water (or even strong heating), hardness salts crystallize, resulting in the formation of deposits on pipes and heaters. Needless to say, what effect scale has on the operation of water heating devices. Therefore, if a boiler, boiler and other equipment are installed in your home, a softening system must be installed.

When using hard water for industrial purposes, calcium and magnesium salts enter into a chemical reaction with other substances, resulting in the formation of harmful products that have a negative impact on the ecological situation.

As you can see influence of hard water on people, the environment and some human activities are more than just negative. In some cases, it can even be fatal - for example, when consumed, stones can form in the kidneys. This means that too hard water must be dealt with by any means.

Water hardness can be temporary or permanent. Temporary appears when rainwater with limestone, bicarbonate salts of magnesium and calcium - bicarbonates are formed. When boiled, they precipitate and form scale. Water with constant hardness contains other magnesium, calcium, potassium and sodium compounds. When boiled, they are not able to precipitate; they must be removed by softening.

Magnesium sulfate and chloride salts are especially harmful: they decompose at high temperatures, releasing sulfuric and hydrochloric acid.

Water hardness in Russia is expressed in milligram equivalents per liter. Soft water has 4 meq / l, semi-hard - 4-8 meq / l, hard - 8-12 meq / l, very hard - from 12 meq / l. The permissible limiting hardness of centralized water supply is 7 mg-eq / l.

Hard water is not recommended for washing and washing dishes, as fabrics will wear out and dishes will tarnish. Great harm Such water causes washing machines, dishwashers, coffee makers and electric kettles: being deposited on heating elements, magnesium and calcium salts form solid lime deposits.

The effect of water hardness on the human body

The World Health Organization (WHO) has not established any severity value for exposure indications. Although studies have found an inverse relationship between water hardness and cardiovascular disease, these data are insufficient for a definitive conclusion. It is also not proven that too soft water can have a negative effect on the balance of minerals in the body. However, high hardness makes the water worse, gives it a bitter taste, has a negative effect on digestion, the body's water-salt balance is disturbed, and various allergic reactions may occur.

As a result of using hard water, there is a significant overconsumption of detergents.

When hard water interacts with detergents (washing powders, soap, shampoos), "soap slags" in the form of foam. After drying, this foam remains in the form on the skin, linen, plumbing. The negative effect of such toxins on the human body is that they begin to destroy the natural fatty film that covers the skin and clog the pores. A sign of such a negative effect is the characteristic "creak" of cleanly washed hair or skin. In this case, it is necessary to use lotions, softening and moisturizing cream.