Jug volume
The volume of the filter jug or the complete container of the tourist filter (see "Type"). In the first case, the total volume of the lower bowl is usually indicated, without a funnel installed in it (the capacity of the funnel can be specified separately). And since the funnel occupies part of the lower bowl, the working capacity of the filter will be less than the claimed volume: for example, if the characteristics indicate a total volume of 3.9 L and a funnel with a capacity of 1.9 L, then in the lower part with the funnel installed, a maximum of 3.9 – 1.9 = 2 liters. In most cases, the working volume of the jug is just a little more than half of the total.
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.
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.
