Corrosion resistant leakproof plastic manhole system

A modular, plastic manhole comprising a plurality of separate, independent, electrically non-conductive units custom installed and permanently configured within an appropriate excavation at a job site proximate an undergound sewer line, said manhole vertically extending between a bottom of the excavation adjacent the sewer line and a surface thereabove, said manhole comprising:

• a leakproof, corrosion resistant base disposed upon said bottom, said base comprising integral, spaced apart, generally coaxial inner and outer shells, each of said shells comprising a cylindrical wall and a floor intersecting said wall, said inner and outer shells defining an annular cavity therebetween for receiving a desired amount of filler;
• corrosion resistant, electrically non-conductive segmented reducer means for flexibly coupling said base to said sewer line;
• at least one leakproof, corrosion resistant, electrically non-conductive riser snap fitted to said base to form a flexible leakproof juncture therebetween, each riser comprising integral inner and outer shells defining an annular cavity therebetween adapted to receive a desired amount of filler, said last mentioned annular cavity separate from said base annular cavity;
• and,
• a leakproof, corrosion resistant cone snap fitted to a riser to form a flexible leakproof juncture therebetween, said cone extending vertically upwardly towards said surface and comprising integral, inner and outer, generally coaxial spaced apart shells defining an annular cavity therebetween adapted to receive a desired amount of filler.