Congratulations! That means your Black Berkey filters have been primed perfectly!
The water flows in a trickle as soon as you fill the top tank. It is the weight of the water column that forces the water through the filters. Once the water column is smaller (between the last third and half), the water flows in a fast drip.
The strength and performance of Black Berkey filters is the microchannels that take a tortuous path so that the water is in contact with the filter over a long distance, but because there are millions of them, the water is ultimately filtered very quickly.
In general, a full tank is filtered in 45 minutes, give or take 10 minutes. If this is not the case, it means that your filters are not primed properly. You must then redo the priming by following the recommendations provided in your manual.
If you find that filtration is really fast (10 to 20 minutes), again, don't panic! The filtration speed indicated by the manufacturer is an average and a very fast filtration does not mean that the filters have failed. First of all, check that your black gaskets are properly installed on the upper tank side and that the blocking plugs are properly in place and tightened (except for the Travel model). Also, make sure the wing nuts are tight enough (but not too tight). After that, when the water is being filtered, check, by lifting the top tank, that the water is flowing only through the end of the threaded rods of the Black Berkey filters. Finally, if after all these verifications made and validated by you, if the filtration is still as fast, you can do a red dye test with the recommendations indicated on your instructions or in our FAQ. This is the ultimate step that will determine if your filters are performing well or not.