Grey & Purple Set for fluoride and chlorine / general filtration. Grey Filter: AlumFlor is an Activated Alumina Fluoride Reduction filter that removes unwanted fluorides from tap water. Fluoride is found in both public drinking water and some bottled waters. This filter’s lifespan is 500 gallons. Purple Filter: This is a triple sediment, taste and odor controlling, chlorine reduction filter, which removes dirt from your water while controlling lime and scale deposits on your valuable equipment. Better taste, better water, better for you.