In plumbing terms, what is 'drainage' typically defined as?

'Drainage' in plumbing refers specifically to the system and process involved in the removal of wastewater and stormwater from buildings and structures. This encompasses the collection, transport, and ultimate disposal of these unwanted fluids, ensuring that they do not accumulate and cause issues such as flooding or contamination within living and working environments. The drainage system is critical because it helps maintain sanitary conditions by directing waste away from inhabited areas, thereby protecting public health.

The other options discuss elements related to plumbing but do not accurately define drainage. For instance, the movement of fresh water to fixtures pertains to water supply rather than drainage. The type of pipe used can vary widely within plumbing systems and is not exclusive to drainage, while chemical treatment of water refers to purification processes and does not directly involve the act of drainage. Thus, option A correctly encapsulates the essential function and purpose of drainage in plumbing.