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.
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.
Cartridge size
The cartridge size indicates both the overall dimensions of the device and compatibility with non-native accessories from other manufacturers. Cartridges differ in width and height, measured in inches. Among the most common options are
5SL (5"x2.5"),
10SL (10"x2.5"),
20SL (20"x2.5"),
10BB (10"x4.5"),
20BB (20"x4.5").
Standard sizes also include
inline cartridges in the form of modules made from white or transparent plastic. They are a sealed cylinder with pre-installed inlet and outlet fittings. Inline cartridges are connected via threaded connections or fittings, simplifying the replacement process. They do not require a separate housing for installation, as their design allows for direct connection to the pipeline or filtration system. They are also slimmer than traditional filters, making a filter with inline cartridges quite presentable in appearance.
Some water purification systems have cartridges in
proprietary sizes that are only compatible with specific filters. These cartridges are ideal for these systems, providing high purification efficiency. They often combine several filtration stages in one element (e.g., mechanical cleaning, chlorine removal, mineralization). This simplifies system maintenance and improve
...s water quality. Proprietary products undergo strict quality control and are tested for compatibility with specific filtering systems, ensuring stable performance. However, there are drawbacks—proprietary cartridges are more expensive and their range is much smaller than universal ones.
