Storm sewers are designed to prevent flooding and transport rainwater that falls in communities via the storm drain system, called a Municipal Separate Storm Sewer System (or MS4 for short) which includes streets, curbing, gutters, catch basins, underground piping, channels, washes, etc. Stormwater is redirected to canals, parks, community lakes, retention basins, and drywells without treatment.

Sanitary sewers take wastewater (from household and commercial uses i.e. sinks, toilets, washers, etc.) and carry it through an underground separate sewer pipe to a wastewater treatment plant where pollutants are removed.