The vent located below the flood level rim of the fixture being vented shall be installed as required for drainage piping in accordance with Article 7, except for sizing. The vent shall be sized in accordance with Section 18-29-916.2. The lowest point of the island fixture vent shall connect full size to the drainage system. The connection shall be to a vertical drain pipe or to the top half of a horizontal drain pipe. Clean-outs shall be provided in the island fixture vent to permit rodding of all vent piping located below the flood level rim of the fixtures. Rodding in both directions shall be permitted through a clean-out.