Purpose
In this case is implied the temperature of the water for which the filter is designed. This parameter is directly related to the maximum operating temperature (see below). In general, modern filters fall into two main categories:
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For cold water. Exactly this purpose that most models today have, regardless of type. This is due to two points: firstly, cold water has to be filtered more often than hot water, and secondly, filter elements for such a temperature are simpler and cheaper. The temperature limit of cold water is usually held at around 40 °C.
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For hot water. Filters designed for connection to hot water systems.
When choosing a filter for its intended purpose, note that the use of “cold” filters with hot water should never be allowed. On the one hand, hot water usually has more impurities than cold water, which reduces cartridge life and cleaning efficiency. On the other hand, high temperature itself is an abnormal mode for filter materials, and instead of water purification, the opposite effect may even occur — the release of harmful substances from the cartridge. Therefore, for such cases, only filters designed for the corresponding temperatures should be selected.
On the other hand, the use of "hot" filters with cold water is quite acceptable — most of these models provide this possibility in case the hot water supply is turned off. However, for cons
...tant work with cold water, it does not make sense to purchase such a filter, if only because it will cost more than the “usual” one.Number of flasks
The number of flasks in the filter makes it clear how many
water cartridges can be installed in it. For a filter for sink, in most cases there are
three flasks. If we are talking about reverse osmosis, then flasks do not mean a membrane, post-filter, etc. since their installation does not provide a separate container. But these types of processing are taken into account in the stages of cleaning. The most obvious difference in the number of flasks is observed in the main filters, where the predominant weight per
1 flask, but there are also
models for 2 flasks or even more.
Pollution clipping
The smallest size of foreign particles (in microns) that the filter can hold in total. Accordingly, the smaller this size, the higher the filtration efficiency, the less undissolved impurities remain in the filtered water. On the other hand, finer cleaning usually takes more time, which affects the speed (throughput) of the filter. It should be noted that in the case of using reverse osmosis filters, the filtration is very fine, up to 0.01 microns.
Filtration speed
The amount of water that the filter is able to pass through itself per unit of time (of course, effectively purified in the process); usually stated in liters per minute. This parameter is largely related to the type (see above): for example, in jugs, the filtration rate usually does not exceed 0.5 L per minute, while for main devices that supply entire apartments, a throughput of tens or even hundreds of liters is required.
Note that it does not always make sense to pursue a high filtration rate. After all, other things being equal, finer cleaning takes more time; accordingly, the faster the filter works, the higher the chance that the quality of such cleaning will be relatively low. And devices that purify water efficiently and quickly usually have an appropriate price. Therefore, it is worth considering the purpose of the filter and, on the basis of this, determine the balance between the filtration speed and its quality when choosing. It is also worth keeping in mind the conditions of use: for example, if you need to filter low-quality tap water for drinking, it is better to sacrifice speed in favor of efficiency.
Max operating temperature
The highest inlet water temperature at which the filter is able to operate normally. Modern filters are conditionally divided into models for cold and hot water: the operating temperature in the first case does not exceed 40 °C, and in the second it can reach 95 °C. For more information on the importance of matching water temperature and filter characteristics, see "Purpose".
Cartridge replacement indicator
Index that indicates the need to replace the filter cartridge or carry out regeneration (depending on the type of device, see above). The specific device of the indicator may be different. So, in inexpensive models, mainly the simplest mechanical calendars are used, where the user need set the date manually. More advanced options may include built-in water meters, colour indicators, and even electronic systems that monitor the actual state of the cartridge. However, this function greatly facilitates the monitoring of the resource depletion anyway (for more details, see "Resource") and reduces the risk of missing the filter element replacement period.
Types of filtration
Substances from which the filter is able to purify water. Some models may also indicate a specific degree of purification in percent for each point; the higher this indicator, the more efficiently the filter is able to cope with its functions. This list will be especially useful if you know what exactly is the most polluted water in your area — it will allow you to choose the model that is most suitable for specific conditions. In addition, in the case of softening systems (see "Type"), this data helps to determine the specific type of device — softener or iron remover.
The most common contaminants today are:
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Mechanical impurities. Particles of small size, insoluble in water and in a state of suspension. An example of such impurities is fine sand.
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Organic impurities. Impurities of various substances of organic origin — benzene, chloroethanes, chlorethylenes, etc. Many of these substances are harmful to humans. Unlike the mechanical impurities described above, "organics" refers to chemical contaminants — such substances dissolve in water, and they have to be filtered at the molecular level. This requires the use of fairly advanced filters. It is also worth mentioning that some types of organic substances — in particular, phenol, pesticides and petroleum products — stand out in separate categories, the possibility of filtering them is specifically stipulated in the specs
...of the filters. This is due to their prevalence and popularity: the term "organic impurities" is not clear to everyone, but the danger of pesticides or petroleum products is well known. See below for details on individual types of organic contaminant.
— Active chlorine. Chlorination is still used in some plumbing systems as a disinfectant. As a result, water supplied to consumers often contains dissolved chlorine, which is harmful to health. Some filters with this function, in addition to chlorine, are also able to remove hydrogen sulfide and other gases dissolved in it, which affect water quality and give it an unpleasant odour. However, these possibilities should be specified separately.
— Iron. Iron is known to many as an important trace element necessary for the functioning of the body; however, a person needs very little of it, and iron impurities in drinking water only harm the body. Note that such impurities can be present in different forms; therefore, different types of filters are required to filter them. So, one of the most famous options is colloidal iron: very small undissolved particles that give the water a characteristic “rusty” colour, as well as a metallic taste and smell. This type of impurities is effectively filtered by osmotic membranes (see "Reverse osmosis"). Also, such membranes cope well with bacterial iron — it is also in the form of insoluble microscopic particles, accumulates a specific type of bacteria that lives in water pipes. But for soluble forms (ferrous hydroxide, chloride and ferrous sulfate), it is necessary to use specialized cleaning and softening systems — iron removers; see "Type" for details. Summing up, we can say that when choosing a device with this type of filtration, it is necessary to take into account the specific form of iron that you have to deal with. At the same time, water can contain several types of such impurities at the same time, which may require complex filtration.
— Ions of heavy metals. In this case, we can also talk about salts of heavy metals: ions are formed when any salts are dissolved in water. Most heavy metals — accordingly, their compounds — are toxic to humans.
— Pesticides. Various chemicals used to combat harmful microorganisms, fungi, weeds, various agricultural pests (insects, rodents), etc. Most pesticides are toxic chemicals and are toxic to humans.
— Nitrates. Salts of nitric acid, which are a common component of mineral fertilizers (saltpeter) in particular. Most of the nitrates are converted into safe compounds during use, but excess fertilizers can end up in drinking water.
— Cadmium. A metal used in particular in anti-corrosion coatings, batteries and inorganic dyes. Poisonous both by itself and in various compounds.
— Petroleum products. Oil and various substances obtained from it (gasoline, kerosene, diesel fuel, fuel oil, etc.). It is poisonous when taken orally.
— Hardness salts. Compounds that give water increased hardness are primarily calcium and magnesium salts. Water purification from such salts is carried out by purification and softening systems based on the principle of ion exchange. For more information about such devices, see "Type", here we note that if the specs of the cleaning and softening system indicate the filtration of hardness salts, then we have a classic softener, if not — an iron remover.
This list is not complete, modern filters can specialize in other types of pollution. For example, for many main models (see "Type"), filtration from sand and clay is separately claimed. In our catalog, such moments are described in the paragraph “Additional cleaning".