Blow molded septic tank method of manufacture

Abstract

A method of forming a septic tank from a blow molded body having an interior and an exterior. The septic tank body is formed from one or more layers of plastic material that are chosen for their chemical, mechanical or other properties. The septic tank body includes a plurality of integral ribs to provide circumferential structurally rigidity and also includes compression molded flange portions to provide axial structural rigidity.

1 . A method of manufacturing a molded septic tank comprising the following steps:
 Forming a parison of molten plastic;   Extruding said parison between two open mold plates, each of said mold plates having a mating surface and an interior mold surface, wherein said extrusion produces a first end and two sides;   Partially closing said mold plates to pinch said parison's first end;   Introducing gas into said parison to partially inflate said parison;   Further closing said mold plates to compression mold a perimeter feature around said parison; and   Further inflating said parison to urge it against the mold plate's interior surfaces.   
   
   
       2 . The method of  claim 1  wherein the step of forming a parison of molten plastic includes the step of:
 preparing a plurality of layers of plastic.   
   
   
       3 . The method of  claim 2  wherein the step of preparing a plurality of layers of plastic includes the step of:
 selecting said layers for their physical characteristics.   
   
   
       4 . The method of  claim 2  wherein the step of preparing a plurality of layers of plastic includes the step of:
 combining at least one of said plurality of layers of plastic with additives from the group consisting of colorants and ultraviolet protectants.