31-1748 Zoeller Simplex Fiberglass Sewage Basin (18" x 30") With 4" Inlet Hub and Anti-Flotation Device (AFD) This fiberglass basin is designed for indoor use in residential, commercial and industrial applications.Watertight and gas tight when properly installedIncludes a 4" inlet hubAnti-Flotation Device (AFD) to reduce or eliminate the basin from popping up out of the ground when the water table is highOne piece, seam free constructionReady to install for economical and simple installationTemperature rated 130 degrees FBasins are not designed to be installed where saturated soil hydrostatic pressure extends above the top of the pit unless the pressure is relieved by an independent drainage system.