Catch basins are typically nestled into the entrance of a drain so that its top is flush with the surface, though basins with curved or arched upper filter surfaces are also used.
Catch basins are important in preventing lake, river and water table pollution by stopping solid materials from clogging drainage systems or by passing through them into bodies of water.
All catch basins have two or more openings; the opening at the top allows for the collection of water and debris, though this opening often features a grid or lattice pattern to prevent the entrance of overly large debris. The other opening or openings are for the actual drained water to exit. These openings are usually covered with another filter; this can be an integral filter or a metal mesh filter that can be removed for cleaning or replacement.
The bottom of the basin features a recession of variable volume which catches and holds debris that should not enter the drainage system. Catch basins are also widely used in home landscaping applications, typically at the entrance to runoff or standing water drainage systems. In that context they prevent small-scale drainage systems from becoming clogged, thereby reducing or eliminating their effectiveness.
Plastic catch basins are more lightweight and inexpensive than metal or concrete catch basins. This makes them easier to install, and for that reason they are popular in consumer drainage system applications. Plastic catch basins are created by plastic injection molding. Injection molding processes begin with a collection of raw plastic materials, or stock, loaded into a hopper. The hopper releases the stock into a conveyance channel where a long screw pushes the stock toward a mold.
A mold is a cavity that, when filled with molten plastic material, creates plastic shapes. After being pressurized and heated in the conveyance channel, the molten plastic is forced into the mold where it is shaped. Then, under carefully controlled conditions, the molded plastic is allowed to cool and harden. At this point, the plastic is cleared of imperfections (if they are present) and then shipped or sent to additional processing.
Plastic basins differ from other plastic containers in that once they are installed, they are intended to function permanently. Unless they are damaged by shifting soil, vehicles passing overhead or if they fail for another reason, they continue to serve their single purpose indefinitely.