A water cooler (10) comprises an internal tank (400) that is normally connected to an inverted reservoir (200) and to a delivery spout (122). A cup shaped filter (300) is placed in the water passage (138, 152, 402) leading from the reservoir to the tank. The filter contains filtration material. It also has microscopic openings (323) in its cover and base (306) through which water passes into and out of a filter cup.