Type
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Jug. Filter in the form of a jug, divided into two halves. Water is poured into the upper half, which looks like a funnel, which under its own weight passes through the filter cartridge to the lower part. Such devices are simple in design and use, as well as low cost. On the other hand, their productivity is low, the capacity usually does not exceed 2 – 3 L, and each time such a filter needs to be filled manually. For an ordinary kitchen for a family of 3–4 people, these shortcomings are not critical, but for large volumes of cooking with intensive water consumption, the filter jug is poorly suited.
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Nozzle on the tap. As the name implies, filters of this type are designed to be installed directly on the spout of a water tap, from the outside. They are easy to connect and use, and in a certain sense more convenient than jugs, because they do not require filling — filtration begins immediately when the tap is opened. Their resource and productivity are also usually higher; in addition, it is worth highlighting the low cost and small size that allowing you to carry the filter with you. Thanks to the latter, among such models there are options that can be installed on a bottle and used as travel filters (see below). The main disadvantages of nozzles are low productivity, as well as the need for regular connection and disconnection, which leads to rapid wear of the attachment.
...— Tabletop. Filters of this variety are separate devices that are installed on the kitchen table (or other suitable surface). They are usually connected to a tap (see "Connection") using a flexible pipe. Such filters are less transportable than the nozzles described above, and are designed for permanent installation in one place. On the other hand, their productivity and resource are usually much higher. An obligatory element in the design of table filters is their own tap (see "Tap").
— Under the sink. Filters designed to be placed under the sink. When installed, they are connected to the water supply (see "Connection"), and a separate tap is brought out to supply filtered water (usually next to the main kitchen tap, but in fact it can be installed anywhere). Such filters usually have a fairly high performance and a good degree of filtration, they are useful for constantly providing the kitchen with filtered water, including for drinking. Of the shortcomings, it is worth noting the difficulty in installation — it requires the participation of a specialist.
— Main (mesh). Main filters are called filters designed to be inserted directly into the water supply system — for example, at the entrance to an apartment. Accordingly, one of the characteristic features of such models is high performance. Mesh — the simplest kind of main filters, equipped with filter elements in the form of a fine mesh, as the name implies. They purify water only from mechanical impurities and are used mainly as a preliminary stage of purification. From models with a cartridge (see below), which can also be used for purely mechanical filtration, models with a mesh are reusable: usually the design provides for the possibility of washing the mesh, restoring its original state.
— Main (with a cartridge). Main filters (see above), which provide the use of replaceable cartridges and are equipped with the appropriate cartridges. Such a design provides more opportunities than mesh models, main filters with a cartridge are capable of providing different types of filtration, including multi-stage cleaning. And the presence of a cartridge in the kit allows you to use the filter right out of the box, without buying additional accessories. At the same time, "native" filter elements are not always optimal, and sometimes a model without a cartridge is more preferable (see below).
— Main (without cartridge). Main filters (see above), which provide the use of replaceable cartridges, but are not equipped with such cartridges. This configuration has its advantages: although the purchase of filter elements requires additional time and money, but you can choose cartridges at your discretion, without relying on the choice of the manufacturer. Sometimes it is easier to collect a filter from a housing and individual filter elements than to buy a ready-made solution.
— Pre-filter. This category includes pre-filters, which are installed not at the entrance to the apartment (as main ones, see above), but in front of a separate household unit, usually a washing machine or dishwasher. Such devices have good performance and are often equipped with water softening systems to prevent limescale formation. The degree of purification in them is relatively low, but this is usually quite enough — since the water in this case is used not for food, but for technical purposes.
— Tourist. Filters designed for use in tourist trips. A common feature of all such models is their small size, which allows you to easily carry the device with you in a backpack or even a pocket. But the design of such a filter may be different. So, some models are containers with filter lids, others are nozzles put on a plastic bottle or other similar container; there are tourist models in the form of a pump capable of pumping water from a stream, lake or other natural reservoir, etc. It makes little sense to buy such a filter for home use, but for “being far from civilization” it may turn out to be simply irreplaceable.
— Cleaning and softening system. Devices designed not only for cleaning, but also for softening water — removing hardness salts and/or dissolved ferrous from it. "Hard" water is undesirable for home use: in particular, it reduces the effectiveness of detergents and leads to the formation of scale in kettles, on heating elements of washing machines, etc. Cleaning and softening systems are divided into two types: actually softeners and iron removers. The first variety uses a special ion exchange resin that traps hardness salt ions (calcium and magnesium) and replaces them with "soft" sodium ions. Such resin must be periodically restored. In iron removers, in turn, a special catalyst is used that oxidizes soluble ferrous to insoluble ferrous — and it is already filtered out mechanically. To which particular variety this or that system belongs — it is worth specifying separately.
— Magnetic. A special kind of main filter installed to the pipeline. However, due to its small throughput, it is not intended for full-fledged water supply, but for connection to household devices, whether it is a boiler, a washing machine or a dishwasher. The main function of these filters is water softeners, which prevents plaque and buildups, it is accordingly prolongs the life of the equipment.
— For shower. Models of filters for installation together with a shower head or in front of a hose. Made in a compact size and have a connecting thread for the hose. This solution will help purify the water (only for one connection point) and get rid of clogged openings in the shower head, because the plaque from contaminated water will be much less.Reverse osmosis
The filter has a water purification system based on
reverse osmosis.
Osmosis is the process of transition of water molecules through the so-called semi-permeable membrane — a barrier that freely passes water molecules, but retains substances dissolved in it. Usually this movement occurs from a solution with a lower concentration of impurities to a solution with a higher concentration, but there are ways to run osmosis in the opposite direction. Purification is based on this: pure water passes through the membrane, and impurities dissolved in it remain behind the barrier.
Since the separation is carried out at the molecular level, the degree of purification during reverse osmosis is very high (for example, salt water becomes fresh, not to mention the fact that the membrane does not allow bacteria to pass through). Another advantage of osmotic membranes is a long service life (see "Resource") compared to conventional filter elements: about several years, usually from 1 to 4. At the same time, reverse osmosis systems are also have disadvantages. For example, their normal operation requires a fairly high pressure, and their performance is lower than with most other filtration methods — to the point that you have to install a storage tank, which accordingly affects the dimensions. In addition, unlike other types of filtration, only about 40% of the incoming water is purified with reverse osmosis, while the rest is draine
...d into the sewer along with the filtered impurities. As a result, this function is found mainly in sink filters and purifiers (see "Type"), where the quality of cleaning is crucial, and large volumes are not required.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.
Stages of purification
The number of purification stages provided for in the filter design. At each stage, water passes through its own filter element, clearing itself of certain contaminants; in this case, the steps are arranged in order from coarser cleaning to finer. For example,
a three-stage system may look like this: the first stage is mechanical removal of impurities, the second stage is the removal of ferrous, and the third is filtration through a carbon cartridge.
The more stages of purification — the more advanced the filter is considered, the cleaner water it usually provides at the outlet. Accordingly, this moment largely depends on the purpose (see “Type”): for example, multi-stage filtration is quite rare in main models, it is practically not used at all in pre-filters, but the number of stages can reach 9 in models for sink.
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.
Resource
The resource can be described as the total amount of water (in thousands of liters) that the filter is able to clean before the cartridge needs to be changed. Usually, it is indicated for a standard filter element (see "Removable cartridges").
Different types of filters (see above) can significantly differ in resource, depending on the features of their application. However, for all models, the rule applies: do not use a cartridge that has exhausted its resource. This is due not only to a drop in filtration efficiency — an “overfilled” filter can begin to release the accumulated contents into the water, further degrading its quality. Since it can be quite difficult to monitor of a specific amount of treated water, many manufacturers indicate the approximate time in which it will be exhausted with an average intensity of use in addition to the resource. Usually it is a few months, but there are exceptions. In addition, for the convenience of the user, various indicators can be provided in the filter design (see "Cartridge replacement indicator").
In models with a multi-stage design (see "Stages of purification"), where there are several cartridges, their resource usually differs, and the total filter resource is usually indicated by the least durable cartridge, that is, until the first replacement of any of the filter elements.
Min. operating pressure
The lowest inlet water pressure at which the filter is able to fully perform its functions. Indicated for models with a connection to the water supply — directly or through a tap (see "Connection").
The design of some filters requires a certain level of inlet pressure for normal operation; if the pressure is insufficient, both throughput and overall filter efficiency suffer, and some functions are not available at all. The latter is especially true for reverse osmosis (see above). Therefore, if the minimum operating pressure is directly indicated in the filter characteristics, you should make sure that your water supply system complies with this parameter before purchasing.
Note that for filters with a booster pump, this column indicates the lowest pressure at which the filter still does not require the use of a pump; see "Pump" for details.
Water mineralization
The presence of a
water mineralizer in the filter design. The mineralizer is usually a container filled with a special slowly dissolving mixture. Thanks to it, filtered water is saturated with various micronutrients: calcium, potassium, fluorine, ferrous (of course, not harmful colloidal ferrous, but another easily digestible form) and others. They have a positive effect on the human body and improve the taste of the water itself compared to completely purified water.
Mineralizers are found mainly in filters equipped with reverse osmosis systems (see above): the fact is that during the operation of such systems, not only harmful impurities are removed from the water, but also the mentioned micronutrients that got there naturally.
Volume of ion exchange resin
The volume of the main working substance used in the water purification and softening system. Note that in this case, we can talk not only about ion-exchange resin, but also about fillers of another type — for example, carbon filters (for more details, see "Type").
In general, this parameter is more of a general reference rather than practical value: manufacturers select the volume of resin in such a way as to ensure the performance claimed for this model. It is natural that the more performant the device, the more filler is required for efficient operation. It should be noted that the amount of resin, even in relatively modest models, is usually measured in tens of liters, which accordingly affects the size and weight.