Storm Drains vs. Sanitary Sewers: Why the Differen

Storm drains and sanitary sewers are often discussed as if they serve the same purpose, but they are designed for fundamentally different types of water. The distinction affects everything from everyday street flooding to how communities protect rivers, lakes, and bays from pollution.

In most municipalities, the stormwater system is built to capture rainfall and snowmelt and route it—directly or with limited treatment—to nearby waterways. The sanitary sewer system, by contrast, is designed to collect wastewater from homes and businesses and deliver it to treatment facilities where it is treated before discharge.