Which component is not included in the definition of a drainage system?

The main public sewer system is not typically considered part of a drainage system as defined by plumbing codes. A drainage system primarily encompasses the internal components and fixtures that manage the removal of waste and wastewater from buildings, which includes the drainage piping and plumbing appliances.

Drainage piping conveys the wastewater from various fixtures to a destination, such as a public sewer or a septic system, and is a fundamental component of the drainage infrastructure. Plumbing appliances, such as sinks and toilets, are also part of the system because they generate wastewater that needs to be drained.

Private drainage networks can refer to the systems that are maintained on an individual property, which handle drainage before it connects to the public sewer system. These components work together to ensure proper waste removal internally within a building or property. In contrast, the main public sewer system operates as a municipal service, which receives the effluent from these drainage systems but is not defined as part of the plumbing drainage system itself. Thus, identifying the main public sewer system as outside the drainage system's definition aligns with plumbing regulations and practices.