DIAGNOSIS This is not normal flow for primed filters. The issue is almost always incomplete priming, leaving an airlock in the filter elements.
FIX Step 1: Remove the filters from the upper chamber. Step 2: Submerge them completely in a bowl or sink of water. Step 3: Vigorously shake and tilt them underwater until no more bubbles emerge. Step 4: Reinstall the dripping-wet filters into the chamber. Step 5: Immediately fill the upper chamber with water. Flow should be a steady stream, not a drip.
IF THAT DIDN'T WORK Verify you are using the correct number of filter washers. Each Black Berkey filter requires one rubber washer installed on the stem, between the filter and the chamber's nut.
HEADS UP Do not let the filters dry out after priming before first use. This can re-create the airlock.