30" sq. x 12" catch basin with lip

Rainwater surface drainage is typically performed by the use of Catch Basins, or sometimes referred to as Inlets. The Catch Basin is a belowground box structure with a horizontal opening at ground level, where a perforated grate is placed to allow rainwater to enter into the Catch Basin box. The grate is made of a material that best fits the intended use of the surface level. Generally, a parking lot would utilize a cast iron grate that is rated for vehicular rating. For pedestrian areas, a light duty grate can be used.

During a rain event, stormwater drains from the surface area into the grate openings of the Catch Basin. This water then drains into a sewer pipe that is connected to the Catch Basin box structure. The stormwater sewer piping is placed at a downward sloping gradient to encourage water to flow through the piping; this is also known as “gravity-flow”. Catch Basins can be linked up with pipe to create a network of drainage points.