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 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".
Replacement cartridges
Models of replaceable cartridges for which the filter is designed. Knowing the names of models, it will be much easier for you to find a replacement for an exhausted cartridge. In addition, the options directly named by the manufacturer are fully compatible with the filter and correspond to official specifications, while there is no such guarantee for "non-native" cartridges.
Several names in this paragraph are usually indicated for filters with multi-stage filtration (see "Stages of purification") — a cartridge for each stage.
Tank volume
The capacity of the reverse osmosis tank. The higher the value, the more water can be filtered for future use. Popular sizes include
a 12 L tank and
a 15 L tank. Only in this case the dimensions for installing the filter will become larger. Accordingly, more is not always better. And yes, it affects the price.
Pump
The filter has its own
pump. This feature is found mainly in two types of filters. The first is reverse osmosis systems (see above): the operation of such filtration requires high pressure, but it is not always achieved at the inlet, and a pump, usually electric, is provided to increase the pressure. The second option is tourist filters (see "Type"), where the pump is designed to draw water from natural reservoirs; they have to be pumped manually.
