How do you know the Black Berkey filters need replacing?

Each Black Berkey element filters a maximum of 11,350 litres of water. Of course, it is very difficult to keep track of the number of litres. In addition, there are some other variables that affect it. For instance, it matters what kind of water is filtered (tap water or water from another source) and how the filters are cleaned. Indeed, cleaning (rinsing under a cold tap and scrubbing with a scouring pad) causes the filters to wear out. Thus, one person naturally scrubs harder than another. You know the Black Berkey filters need replacing when the filter speed has decreased significantly. Normally, re-priming or cleaning the filters will ensure a normal filter speed again. So if they need to be replaced, priming and/or cleaning will no longer ensure filter speed gains. Also, the Black Berkey filters will then fail the red dye test (add 2 teaspoons of red synthetic food dye to the top tank of water and let it filter, the water should be completely transparent at the bottom. If not, they fail). It is then time to replace them.