Abstract: A new water cap with built-in filter and air pump for filtering unfiltered water within a container. The inventive device includes a filtering portion position interiorly of a container. The filtering portion includes an upper microscreen disposed within the open lower end of the conduit. An upper layer of foam is disposed below the upper microscreen. A filtering cartridge is disposed below the upper layer of foam. A lower layer of foam is disposed below the filtering cartridge. A lower microscreen is disposed below the lower layer of foam. An air pump is coupled with respect to the container. The air pump is in communication with an interior of the container. The air pump has a check valve and an adjustable or standard air flow valve in communication therewith.