Storm Drains vs. Sanitary Sewers: Key Differences

At a glance, “storm drain” and “sanitary sewer” can look similar—both are pipes and grates that move water away from streets. But they are designed for different types of water, and sending the wrong kind of flow into the wrong system can lead to pollution, flooding, and costly repairs.

Storm drains are meant to carry rainfall and runoff—think water from storms, melted snow, and surface water that flows across streets, rooftops, and parking lots. Sanitary sewers are built to carry domestic and industrial wastewater from homes and businesses, such as toilet waste, sinks, showers, and certain regulated facility discharges.