The answer to 'what is sewer line' is the underground pipe system that carries wastewater and sewage from a home or building to the municipal sewer system or a septic tank. The sewer line is responsible for transporting all of the used water and waste from sinks, toilets, showers, and other plumbing fixtures out of the home and into the larger sewage network.
Sewer lines are typically made of cast iron, PVC, or clay pipes and run from the home's plumbing system to the street or property line, where they connect to the city's main sewer line. Proper maintenance and regular inspections are important to prevent clogs, leaks, and other issues with the sewer line.