The best way to gauge when to replace the Berkey PF-2™ Elements is to do the following:

1. Keep a track of how many times per week you need to refill your system.
2. Then multiply that figure times the capacity in liters of your particular system (for example the Berkey light system is 10.40 liters) to determine total liters used per week.
3. Finally divide the total liters used per week into the 3.785 liters and that will tell you how many weeks before the filters should be replaced.
4. Next calculate the future date for replacement (52 weeks per year) and write that date on a sticker and attach it to the bottom of your system for future reference.