In plumbing, what does the term "drainage" refer to?

The term "drainage" in plumbing specifically refers to the removal of wastewater and other liquid waste from a plumbing system. This process is crucial for maintaining sanitation and hygiene within residential and commercial buildings. Drainage systems are designed to transport waste fluids away from fixtures such as sinks, toilets, and showers, directing them to sewer or septic systems.

This function is essential to prevent backflow, clogs, and other issues that can arise from improperly managed waste. It's a fundamental aspect of plumbing that ensures a safe and functional environment for users.

The other choices do not relate to drainage as a plumbing term; for instance, the storage of clean water pertains to water supply systems, filtering water before use involves water treatment processes, and collecting rainwater for reuse falls under water conservation practices. These concepts, while important in the broader context of plumbing and water management, do not define drainage.