The plunger pump is a positive displacement pump, designed to pump high solids (18-20% solids) content commonly found in raw influent. This technology is specified to pump effluent (run off) and industrial discharge as well. Together with progressive cavity pumps which have been in existence since the 1930’s, the plunger pump first began pumping municipal sludge in the 1920’s. As of 2009, there are over 18,000 plunger pumps in operation worldwide. Where are plunger pumps installed A plunger pump is typically installed in a pump house or raw sludge transfer station located close to influent sewers, sedimentation tanks and digesters.