The life span is either 3,800 litres of water or one year, whichever comes first.
Knowing when the filters need to be replaced is a simple calculation, explained in more detail below:

- Let's say you are using a Big Berkey® model with 2 Black Berkey® filters + 2 PF-2 filters,
which are filled once a day, the calculation is as follows: 3800 / 7.3 / 365 = 1.42 years. In this case, you should replace the PF-2 filters after one year.

- For two filterings per day, adapt the above calculation: 3800 / 7.3x2 / 365 = 0.71 years or 8 months. In this case, you should replace your PF-2 filters after eight and a half months.

This calculation must be adapted according to the model used and the frequency of filling.