Find Your Sewershed


The City of Pittsburgh is primarily composed of combined sewers (darker green areas on the map) which mean that storm water and sewage are carried in the same pipe. The average rain event will cause this system to reach capacity and overflow, discharging a mix of stormwater and sewage into the rivers. This is known as a Combined Sewer Overflow (CSO).

If you click on a sewershed you will see baseline CSO statistics PWSA calculated using a system wide model developed to simulate ALCOSAN’s typical year flow conditions. Typical Year (TY) is the modified version of precipitation measured during the 2003 calendar year that ALCOSAN uses and was used during this analysis. 

Type in your address in the search bar above to find out what sewershed you live in and how much your sewershed contributes to overflows into our rivers. A sewershed closely follows watershed boundaries, referring to an area of land in which all water naturally drains to the same point.

You can make a difference and help reduce this volume! 

Green infrastructure allows rain to soak into the landscape and stay out of the sewer pipes. Learn more about how you can incorporate green infrastructure on your property and in your community here

Conserving water can have positive impacts on the issues caused by CSOs. If water use is conserved during rain events, the volume of CSO will be reduced. Taking this additional sanitary sewer flow coming from homes and businesses out of the combined sewer system will provide more volume for the system to manage stormwater. 

Here are some ways you can reduce stress on the system during storm events:

  • Do laundry later

  • Take a shorter shower (or take one later)  

  • Delay dishwashing

  • Wait to flush the toilet


Here are some ways you can conserve water every day:

  • When doing laundry, always wash full loads

  • Same applies to washing dishes (using the dishwasher) - only run if full

  • If washing dishes by hand, fill up the sink instead of leaving the water running

  • When it's time to replace the clothes or dish washer, choose a high efficiency washer with a low water factor

  • Check water bills for high water use instances to identify leaks

  • Use low-flow shower heads and faucet aerators to reduce water use

  • Don't leave the water running when brushing your teeth

  • Use a broom to clean your driveway or sidewalks instead of hosing them down

  • Set up a rain barrel to reuse water for irrigating your lawn and plants

If you live in a separated area, the lighter green areas on the map, you can help improve water quality!

Although the separate sewer system does not pose immediate environmental hazards (like combined sewer systems discharging untreated sewage), it does degrade the water quality. Stormwater collected in these pipes are not treated before being discharged into the rivers. As stormwater runoff flows over roads, rooftops and other impervious surfaces it collects debris, waste, salts, eroded soils, and other bacteria/metals polluting the water. Learn what you can do to help  our rivers here! 



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