Diagnosis
This is almost always a seating issue with the filter element's washer, not a crack. The black rubber grommet (the sealing washer) isn't seated flat or the filter isn't screwed in tight enough.
How to Fix It
First, unscrew and remove the filter. Check that the black rubber grommet is properly seated in its groove on the filter stem—it can pop out during shipping. Make sure it's clean and pliable. Hand-tighten the filter into the receiving nut in the bottom chamber. You need to give it a good, firm turn—think "snug," not "Hulk smash." It should feel solid. Fill the upper chamber and check for drips.
If That Didn't Work
Inspect the white receiving nut in the bottom chamber for hairline cracks, which can happen from overtightening. If it's cracked, you'll need a replacement nut and washer kit from Berkey.
Heads Up
Don't use tools or excessive force to tighten the filters; you'll crack the plastic nut. The seal is made by compressing the rubber washer, not by threading the plastic until it strips.