Water filters and germs - what you have to consider

Water filters are used in many areas for the qualitative improvement and treatment of drinking water. If and when water filters are also able to filter out germs and what to look for to prevent bacterial contamination of water filters is explained here.

Germs in water filters

Water can contain not only bacteria but also other pathogens. These are:

  • virus
  • prions
  • Protozoa and microparasites
  • mushrooms

At a certain filter size, water filters can also filter out some of these pathogens. As a rule, bacteria and protozoa can be filtered out reliably from a filter pore size of 2 μm.

But that does not apply to viruses, nor to prions. They are too small to be retained by mechanical filters. They can only be rendered harmless by disinfection (decoction or UV disinfection).


Prions are infectious proteins that can trigger various diseases, such as Creutzfeldt-Jakob disease or BSE in humans. Currently, several other diseases are suspected to be triggered by altered prions from the animal kingdom.

Prions can also be in the sewage. Their inactivation or filtering is currently not possible because they are not life forms but mere proteins.

Germination of water filters

Microbial contamination is a major risk for water filters. Above all with activated carbon filters, but also with other filters, bacterial cultures can accumulate and multiply in the water filter.

With a very full filter, you can "break through" the pressurized water and create an acute contamination.

It is therefore important to have a regular and timely filter exchange, if possible before the filter is full. If this is overlooked or disregarded, water filters can become a very high risk. The infection limit of around 10,000 CFU / 100 ml can be exceeded very quickly with undisturbed bacterial growth in the filter.

The only real protection against breaking bacterial cultures is offered by reverse osmosis systems. However, they use a lot of energy and water for flushing (about 3 liters of water for 1 liter of purified water). In addition, they produce a not necessarily suitable for drinking water.

Tips & Tricks

The risk of breaking the filter under pressure is not only with bacteria, but also with other pollutants, when they accumulate in the filter. This should be noted.

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