Machinery is required to handle both products. In addition, installation speed is more dependent upon rate of excavation than pipe placement. The heavier weight of concrete also is an advantage when flotation is a concern. It is well documented that the comparative lighter weight of flexible pipe makes it subject to lateral movement when compacting on the sides of the pipe. HDPE also tends to lift vertically off the required grade as material under the haunches is compacted.
Select material is important to a successful installation of flexible pipe.
HDPE installation procedures recommend that the trench width be established by the designer and ASTM D2321 requires all material in the haunch area be placed by hand. The increased number of joints is a perceived shortcoming of concrete pipe while in fact it may be an advantage. Line and grade is maintained and checked frequently. Various joints and gasket designs are available for most installation conditions from culverts, to storm sewers, to sanitary sewers. Concrete pipe is available in several different classes and shapes for each diameter.