A sewer

Sewers are underground pipes that take away dirty water and human waste from homes, offices and many other places. Sanitary sewers lead to sewage treatment plants that remove the harmful and unwanted parts, returning clean water to the environment. Many rules and regulations exist for how clean the final discharge (effluent) must be. Storm sewers are usually simpler. Houses that do not have a connection to city sewer will have a septic tank.