A drainage system is a network of channels and pipes that redirect excess water away from an area. Drainage systems can be divided into two categories: surface and subsurface. Each category has several components with similar functions but different names. The components of a surface system include the main collection ditch, field ditch, and field drain, while the components of a subsurface system include the main, submain, and lateral conduits from the submain.

A surface drainage system utilizes ditches or channels to collect and remove water from an area. The ditches or channels direct the water toward the main drain, which is designed to absorb excess water and mitigate flooding. These systems are typically used on properties with slopes or hills since the lay of the land is ideal for implementing this system.

Subsurface drainage systems are designed to collect and remove water that has seeped below the surface and is collecting at the root zone of plants. French drains are one of the types of subsurface drains that are often used to collect and remove water from areas that are prone to flooding.

In plumbing, a drainage system consists of piping that conveys sewage, rainwater, or other liquid waste to a point of disposal, either in the sewer system or septic tank. Its main objective is to collect and remove wastewater and keep sewer gases out of the building. Unlike the piping that brings water into a building, the piping for a drainage system is usually made of plastic or metal.