In plumbing, what does "drainage pipe" primarily transport?

The term "drainage pipe" refers to a specific type of pipe system primarily designed to transport wastewater away from various sources, such as sinks, toilets, and showers, towards the municipal sewer system or a septic tank. Wastewater includes not only human waste but also gray water from household activities. This specific functionality is crucial in maintaining sanitary conditions within buildings and preventing contamination of potable water sources.

While pipes do indeed transport water, a drainage pipe's main purpose is not to carry hot or cold water used for other tasks but rather to ensure the efficient removal of waste products. The transportation of air is also not a function associated with drainage pipes, as they are not designed to facilitate ventilation or air flow. Thus, the primary role of drainage pipes is encapsulated in their function of directing and managing wastewater effectively and safely.