Abstract: A filtering device for a gravity-flow liquid treatment system includes a first filter component that can be either exposed or adjacent to a substantially transparent region in at least a portion of a filter housing. The first filter component is capable of providing a visual indication of exposure to at least one contaminant. The contaminants for which the first filter component can indicate exposure include particles, inorganic, and organic contamination. Particle contamination is indicated by a change in color of the first filter component through particle collection. Inorganic and organic contaminants are indicated by reaction with at least one agent capable of undergoing a color-change reaction in response to at least one contaminant.

Abstract: A gravity flow carbon block filter comprising approximately 20-90 wt % activated carbon particles having a mean particle size in the range of approximately 90-220 ?m, and approximately 10-50 wt % low melt index polymeric material. The low melt index polymeric material can have a melt index less than 1.0 g/10 min or greater than 1.0 g/10 min and a mean particle size in the range of approximately 20-150 ?m.

Abstract: A filtering device for a gravity-flow liquid treatment system includes a first filter component that can be either exposed or adjacent to a substantially transparent region in at least a portion of a filter housing. The first filter component is capable of providing a visual indication of exposure to at least one contaminant. The contaminants for which the first filter component can indicate exposure include particles, inorganic, and organic contamination. Particle contamination is indicated by a change in color of the first filter component through particle collection. Inorganic and organic contaminants are indicated by reaction with at least one agent capable of undergoing a color-change reaction in response to at least one contaminant.