A fluid-filtering apparatus includes an upper cartridge and a lower cartridge. The upper cartridge includes a permeable fluid-filtering first tube that surrounds and extends along an axis and that defines a first-tube cavity. An axially-extending permeable fluid-filtering second tube is located within the first-tube cavity and defines a second-tube cavity. The lower cartridge includes an axially-extending impermeable third tube that defines a third cavity. An axially-extending permeable fluid-filtering fourth tube, of the lower cartridge, is located within the third cavity and defines a fourth-tube cavity. The upper and lower cartridges are coupled together and contained within an impermeable casing.