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A water filter is a system designed to remove pollutants from water to make it purer. It is a generic term that encompasses various devices and techniques, primarily used for filtering tap water in household use. A water purifier is designed to purify water similarly to a water filter, with the key difference being its ability to remove certain specific elements that a simple water filter cannot.

Water Filter vs. Water Purifier: What's the Difference?

In addition to a range of pollutants that a water filter can remove, depending on its design, a water filter should be capable of eliminating bacteria and protozoa. Protozoa are small, often solitary organisms present in water, some of which are parasites responsible for diseases such as malaria or certain types of dysentery.

A purifier, on the other hand, can remove viruses in addition to bacteria and protozoa.

Water Filter or Water Purifier - Berkey® France Millenium
Bacteria Protozoa Viruses
Water Filter ✖️
Water Purifier

But to be classified as a water purifier, a device must not only filter viruses or bacteria but must do so at a specific removal rate. For bacteria, Klebsiella Terrigena is chosen as the test population. This bacterium is often found in unpolluted soil or surface waters. For viruses, the test uses a rotavirus (responsible for gastroenteritis) and the polio virus. The removal rate for bacteria must exceed 99.9999% (log-6) and 99.99% (log-4) for viruses.

The "log" scale is used to quantify the filtration level. "log-2" means a filtration level between 0 and 99%. "log-3" indicates a filtration level between 0 and 99.9%. "log-4" indicates a filtration level between 0 and 99.99%, and so on. Which means, if the filtration level for bacteria is at log-3, it means a system with this precision lets through 10 times more bacteria than a system rated at log-4.

Berkey® systems have been evaluated on this basis, and the results are available in the following table.

Standard Removal Rate (norm)

Berkey® Removal Rate

Bacteria > 99.9999% (log-6) 99.9999999% (log-9)
Viruses > 99.99% (log-4) 99.99% (log-4)

The Black Berkey® filter elements used in all systems meet and even exceed the standards for water purifiers. Moreover, Berkey® systems' bacteria removal is 1000 times higher than the recommended standard.

By eliminating 99.99% of viruses, the Berkey® purification system is actually the only autonomous water purifier on the market.