The lifespan is 3,800 liters of water or 1 year, whichever comes first. To determine when to change the filters, simply perform the following calculation:

- Assuming the use of a Big Berkey® model equipped with 2 Black Berkey® filters and 2 PF-2 filters, filled once a day, the calculation will be as follows: 3800 / 7.3 / 365 = 1.42 years. In this case, you should change your PF-2 filters after 1 year.

- Assuming 2 filtrations per day, you adapt the above calculation: 3800 / 7.3x2 / 365 = 0.71 years or 8.5 months. In this case, you should change your PF-2 filters after 8.5 months.

This calculation should be adjusted according to the model used and the frequency of refills.