Small-scale sewage pumping is normally done by a submersible pump. This became popular in the early 1960s, when a guide rail system was developed to lift the submersible pump out of the pump station for repair, and ended the dirty and sometimes dangerous task of sending people into the sewage or wet pit. Growth of the submersible pump for sewage pumping since has been dramatic, as an increasing number of specifiers and developers learned of their advantages. Three classes of submersible pumps exist: Vertical type sewage pumps have also been used for many years.