Water treatment cartridges and processes related thereto

An embodiment is directed to a water treatment cartridge for treating drinking water. The water treatment cartridge may comprise a housing, an inlet for introducing water into the water treatment cartridge, an outlet port for egress of water from the water treatment cartridge, and a first treatment material. The first treatment material may have a core region. The water treatment cartridge also may have a second treatment material. The second treatment material may be contained within the core region of the first treatment material, such that the first treatment material and the second treatment material are in direct contact and direct communication. The second treatment material may be a calcium source. The water treatment cartridge also may have a liquid-pervious retainer. The retainer may cap the outlet port and may extend into the second treatment material. Water may enter the water treatment cartridge via the inlet, the water may then radially enter the first treatment material, then radially flow through the first treatment material, then, at least a portion of the water may radially enter the second treatment material, then axially flow through the second treatment material, then egress the water treatment cartridge via the outlet port.