Some toilets have been found to be leaking from the bottom of the U bend due to hairline cracks on the ceramic or for being porous due to inadequate glazing of the ceramic before being kilned. These defective toilets include some leading brands. In most cases the leaks are so minor or it takes a long period before the cracks to widen that it may take a year or more before enough moisture builds-up under the toilet for it to be observable as it flows out from the base.