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.
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.
Max. operating pressure
The highest inlet water pressure at which a filter connected to a tap or water supply can operate indefinitely (at least until the resource is exhausted, see above) without breakdowns, failures, etc. In other words, this is the ultimate strength of the filter. Therefore, this parameter has a great importance, and when choosing a filter, you must make sure that it meets the characteristics of the connection point. In this case, it is best to choose a model with a margin: although the device will not break from short-term pressure surges in excess of the working device, but this will create off-design loads and can lead to early failure.
When buying a filter for ordinary domestic use, it can be assumed that the maximum pressure in the water supply, provided for by the housing and communal services standards of most post-Soviet countries, represents 6 atm, but its actual value is usually lower. Therefore, 6 atm filters are quite suitable for the definition of a “model with a margin” for apartments with medium and especially low water pressure.
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".
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.
Salt tank capacity
The capacity of the tank in which the saline solution is prepared for the regeneration (recovery) of the ion exchange resin in the cleaning and softening system (see "Type").
The process is described in detail in paragraph "Regeneration". Also note here that the saline solution for recovery is first accumulated in a special tank, and only then it is supplied to the resin washing. The capacity of such a tank (salt tank) is generally a reference parameter: manufacturers select it in such a way as to ensure optimal functioning in regeneration mode. We only note that this volume is usually quite solid — it is several times larger than the volume of the filler itself (although the capacity of the salt tank is indicated in kilograms, but in this case it is quite possible to assume that 1 kg approximately corresponds to 1 L).
Salt consumption for regeneration
The amount of salt consumed by the cleaning and softening system (see "Type") for one regeneration (recovery) of the ion exchange resin.
For more information about the point of this procedure, see p. "Regeneration". And consumption data allows you to determine how much salt you need to have "in the household" for effective recovery of the filler. At the same time, in systems with automatic and programmable regeneration, the corresponding amount of salt is filled in advance and consumed if necessary.
Water consumption for regeneration
The amount of water consumed by the cleaning and softening system (see "Type") for one regeneration procedure.
For more information about the point of this procedure, see p. "Regeneration". It requires salt and water, and in some models — only clean water. At the same time, after washing, anyway, it cannot be used in the household and is drained into the sewer.
Information about water consumption will be useful primarily to those who use metered water supply, as well as to those who fundamentally intend to save water (or are forced to do so for one reason or another). Note that for regeneration, the filler must be subjected to repeated washing, due to which the water consumption is several times higher than the volume of the filler. At the same time, this ratio can vary greatly for different models: for example, with a filler amount of 25 L, the consumption can be 0.25 m3, and 0.8 m3, and even more than a cubic metre.
Regeneration time
The time spent by the cleaning and softening system (see "Type") for the regeneration (recovery) of the filler.
The point of the procedure itself is described in detail in paragraph "Regeneration". Here we note that the device cannot be used during the recovery process; and since softeners are usually installed directly into the water supply (see "Connection"), then for this time you can be left without water at all. Knowing the duration of regeneration, you can plan it in such a way that it does not cause discomfort — for example, carry out the procedure at night.
At the same time, it is worth noting that some advanced softeners have a twin design with two filler blocks. When one block is regenerated, the system switches to the second one, which is ready, and works on it until this block also needs regeneration, after which the roles change — the first block that has managed to recover is put into operation. This format of work provides a constant supply of water without interruptions for regeneration, however, such devices are also expensive.
