Abstract: Method for filtering treated water and apparatus to practice the method. The method taught herein consists of filling a first container with water, attaching a special filter apparatus thereto and finally attaching a second, empty bottle to the filter apparatus. When the conjoined containers and filter apparatus are inverted, the water in the first container, now atop the filter apparatus passes through that apparatus and into the second container under the impetus of gravity. Air displaced from the second container by the transfer of water therein is exchanged into the first container by means of a vent located in the body of the filter apparatus. The apparatus taught herein comprises a filter body having disposed within the previously discussed vent, at least one filter element and a check valve to preclude the unwanted re-filtration of previously filtered water.