Q: What is the difference between a Stormwater System and a Sewer System?

A: These two systems are completely different.

Stormwater System
Water that flows down driveways and streets and into a gutter goes into a storm drain that flows directly to a lake, river or the bay. This water often picks up pollutants along the way. These pollutants can have harmful effects on drinking water supplies, recreational use, and wildlife.

Sewer System
The water that goes down a sink or toilet in your home or business flows to a wastewater treatment plant or to your on-site septic system, where it is treated and filtered.

Q: What is allowed in the storm sewer?

A: Unless identified as a significant source of pollutants to the States’ waters, the following are not prohibited from entering the storm sewer system as long as they are identified and control measures are developed to minimize the impact of such sources:

   - Water line flushing
   - Landscaper irrigation
   - Diverted stream flows
   - Rising groundwaters
   - Uncontaminated groundwater infiltration to separate storm sewers
   - Uncontaminated pumped groundwater
   - Discharges form potable water sources
   - Foundation Drains- Air conditioning condensate
   - Irrigation water
   - Springs
   - Water from crawl space pumps
   - Footing drains
   - Lawn watering
   - Individual residential vehicle washing (see “How You Can Help”)
   - Flows form riparian habititats and wetlands
   - Dechlorinated swimming pool discharges
   - Street wash waters
   - Discharges or flows from emergency fire fighting activities


      EPA’s NPDES Frequently Asked Questions