Berkey® systems are not just simple water filters. They are efficient water purifiers that remove a significant number of pollutants, viruses, and bacteria. The list of these contaminants is published and available through analyses conducted by an independent laboratory following NSF protocol standards. These results are available to the public and can be found here: list of pollutants removed by Berkey® filters

When you want to filter water but composition is totally unidentified, and if do not have the choice (such as in an emergency situation), we recommend performing an initial analysis to ensure that there is no specific contamination that the Berkey® system may not be able to filter properly. This could be particular industrial pollution, resurfacing of old pollution, significant radioactive contamination, etc. The risk is indeed low, but the manufacturer Berkey® itself advises filtering the safest water possible or conducting tests beforehand. This does not take away from the exceptional performance of Berkey® filters and their actual ability to purify water. It is simply a precautionary procedure.

If you have or have not decided to perform preliminary water analysis, two points must be verified:

- Ensure that the seal is perfect from the first filtration. The wing nuts and blocking plugs must be sufficiently tightened so that the filtered water exits only through the ends of the threaded rods and not around the nuts or plugs. To do this, you must lift the upper chamber and visually check that everything is functioning properly.
- It is also recommended to perform the red dye test from the second filtration.
- None of the elements except the inside of the upper chamber and the top part of the filters should come into contact with contaminated water.
- Pay attention not to wash your hands with this water, if not you will contaminate any parts you touch: tap, filters, lower chamber.
- Under these conditions, Black Berkey® filters should not be primed with the contaminated water. They must be primed with the Black Berkey® Primer pump. This is a compulsory tool for these conditions.
- Throw away the first 2 filtrations.

You can also refer to this topic for more information on filtering rainwater.