Sioux Chief 869 series ProCheck backwater valves shall be used where necessary in drainage systems. Backwater valve shall be installed in horizontal drainage lines to reduce or prevent damage to dwelling from sewage backup. Backwater valve shall have a stepped design to provide adequate fall through the valve body and encourage flow. Flapper shall install into valve body via removable carrier, which utilizes key-to-slot to ensure proper alignment. Flapper shall have a permanent, one-piece sealing surface, and allow unrestricted, unidirectional flow. Valve body shall be sealed by an impact/solvent resistant lid with o-ring