Curb Inlet

When designing or building new streets and parking areas, a curb inlet is used to assist in the stormwater drainage of the paved surface area. The curb inlet consists of a first-stage belowground box structure with a second stage horizontal throat opening that is flush with the paved surface. As the name implies, the throat opening is placed along the street curb perimeter. Internal access to the inlet structure is provided by an iron manhole cover. Storm sewer pipe is connected to the inlet structure to provide for drainage out of the structure. Often, the curb inlet structure is used a junction point when an incoming drainage piping is connected. During a rain event, stormwater drains from the street paved area into the throat opening of the curb inlet. This water continues to drain into a sewer pipe that is connected to the curb inlet 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.” The stormwater eventually flows into a stream, river, ocean, or type of public estuary.