下水道是现代都市公共设施之一，在古罗马时期就已经出现。以功能可分为污水下水道和雨水下水道。

• 污水下水道是将污水运往污水处理厂的系统。

公共污水下水道

• 由家庭所制造出来的污水

专用污水下水道

• 工厂制造的污水

Sewerage is the infrastructure that conveys sewage. It encompasses components such as receiving drains, manholes, pumping stations, storm overflows, and screening chambers of the combined sewer or sanitary sewer. Sewerage ends at the entry to a sewage treatment plant or at the point of discharge into the environment. It is the system of pipes, chambers, manholes, etc. that conveys the sewage or storm water.