FIT Top is designed not to leak. Often it's just that the user has neglected to seat the filter flush with the housing. Push the filter (under the hinge) down until the surfaces are flush and the top O-ring disappears inside. Also, make sure you close the drinking spout cover snugly. The colored cup glued to the bottom of the FIT Bottle can also catch some overfill or drips making you "think" the bottle is cracked at the base. It is not and you can even remove that decorative cup if you wish. Sometimes a few drips escape between the bottle and FIT Top when the bottle opening is not perfectly flat. They run along the threads and out under the lid. Most bottles are flat and do NOT drip. If yours does, please contact us and we will mail you a FREE large O-ring that inserts between the bottle and FIT Top to 100% eliminate this issue.