# Outfall

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Discharge point of a drain or waste stream into a body of water

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Outfall with a flap valve at [River Thames](/source/River_Thames) in London

An **outfall** is the discharge point of a [storm drain](/source/Storm_drain) or waste stream into a body of water. In the United Kingdom, the term may also apply to discharges from a "[watercourse](/source/Watercourse)", which may be a river, stream or canal.[1]

## United States permit requirements

Outfall from a sewage plant discharging to [Passaic River](/source/Passaic_River) in New Jersey

In the United States, [point sources](/source/Point_source) may not discharge [pollutants](/source/Water_pollution) to surface waters without a permit issued through the [National Pollutant Discharge Elimination System](/source/National_Pollutant_Discharge_Elimination_System) (NPDES), as required by the [Clean Water Act](/source/Clean_Water_Act).[2] Most NPDES permits are issued by state environmental agencies. The [U.S. Environmental Protection Agency](/source/U.S._Environmental_Protection_Agency) (EPA) issues permits in some locations.[3]

Point sources include industrial facilities; [service industries](/source/Service_industries); [municipal governments](/source/Local_government_in_the_United_States) (particularly [sewage treatment plants](/source/Sewage_treatment_plants) and [stormwater](/source/Stormwater) outfalls); other government facilities such as [military bases](/source/List_of_United_States_military_bases); and some agricultural facilities, such as animal [feedlots](/source/Feedlot).[4]

Further information: [United States regulation of point source water pollution](/source/United_States_regulation_of_point_source_water_pollution)

## See also

- [Combined sewer](/source/Combined_sewer)

- [Greywater](/source/Greywater)

- [Marine outfall](/source/Marine_outfall)

- [Night soil](/source/Night_soil)

- [River mouth](/source/River_mouth)

## References

1. **[^](#cite_ref-1)** ["Structure: Outfall"](https://environment.data.gov.uk/asset-management/drl-app/revision/current/categories/Structure/asset-types/Outfall). Bristol, UK: United Kingdom Department for Environment Food & Rural Affairs. 2025-04-06.

1. **[^](#cite_ref-2)** United States. [Pub. L.](/source/Act_of_Congress#Public_law,_private_law,_designation) [92–500: Federal Water Pollution Control Act Amendments of 1972](https://uslaw.link/citation/us-law/public/92/500) Approved October 18, 1972.

1. **[^](#cite_ref-3)** ["National Pollutant Discharge Elimination System"](https://www.epa.gov/npdes). Washington, D.C.: U.S. Environmental Protection Agency (EPA). 2025-06-03.

1. **[^](#cite_ref-4)** ["NPDES Permit Basics"](https://www.epa.gov/npdes/npdes-permit-basics). EPA. 2025-06-03.

v t e Sewerage Types Combined sewer Decentralized wastewater system Drain-waste-vent system Effluent sewer Force main Gravity sewer Outfall Pressure sewer Sanitary sewer Simplified sewerage Storm drain Vacuum sewer Construction materials Asbestos cement pipe Brickwork Cast iron pipe Concrete pipe Culvert Interceptor ditch Plastic pipe Reinforced concrete Steel pipe Vitrified clay pipe Related equipment Chopper pump Combined sewer overflow Grease trap Grinder pump Maceration Lift station Sanitary manhole Sewage pumping Sewer gas destructor lamp Stormwater detention vault Submersible pump Sump pump Trap Problems Biogenic sulfide corrosion Blockage Fatberg First flush Infiltration/Inflow Sanitary sewer overflow Sewer fly Sewer gas Sewer rat Liquids transported Blackwater (waste) Greywater Industrial wastewater Sewage Stormwater Background History of water supply and sanitation

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