of the inlet outlet cap 6 and down into the sump portion 4 the water then flows radially into the exterior of the tubular filtration cartridge 8 through the filtration substance 10 where particulate matter is removed and is discharged into the central axial chamber 16 of the tubular filtration cartridge 8 the incoming water flows upward along the chamber 16 and contacts the feeder insert 18 disposed within the axial chamber 16 a portion of the incoming water flows through the flow holes 26 in the upstream end cap 24 and into the upstream containment chamber 20 contacting the feed chemical 22 contained within the remainder of the incoming water flows around the upstream containment chamber 20 to the metering slots 30 located on the upstream end of the downstream flow bypass chamber 28 and into the bypass chamber 28 the water flow entering the upstream containment chamber 20 and the water directly entering the downstream flow bypass 28 recombine in the downstream flow bypass chamber 28 the recombined water then flows outward from the downstream flow bypass chamber 28 and into the outlet end of the inlet outlet cap 6 for discharge to the household water outlets the feed chemical 22 can be any slow dissolving substance that performs a secondary purification or disinfection function on the incoming water most typically the chemical used is a halogenated ion exchange resin the halogen most often used in these halogenated ion exchange resins is iodine in a tri iodide or penta iodide form while the exact mechanism is not completely understood the iodine in the resin interacts with the cell membranes of bacteria present in the incoming water supply affecting the cell membranes of all.