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Leave A Mark!

Across our city, there are aproximately 75,000 inlets collecting stormwater. As rainwater and melting snow washes over our gardens, sidewalks and streets, it picks up pollutants and trash that ends up in these drains, but where does it drain to?

A - Separate Sewer System

B - Combined Sewer System

(A) Is an example of a separate sewer system. Separate sewers are newer and have two separate pipes, one for stormwater and one for waste from homes and businesses. Inlets connected to this type of sewer collect only stormwater and discharge it directly to local creeks and rivers

(B) Is an example of a combined sewer system. This older type of sewer has only one large pipe that collects both stormwater and waste water from homes and businesses. Inlets connected to this system drain into this central pipe. During larger storms the flow of stormwater can exceed the capacity of the system causing the sewer to overflow into our creeks and rivers!


Many Philadelphians don’t realize that what goes down our storm drains eventually makes its way into our creeks before draining into the Delaware and Schuylkill rivers, the source of our drinking water! 

Philadelphia Water is working hard to protect our waterways by preventing stormwater runoff, but we need your help. By marking storm drains, you’re playing an important role in protecting our waterways and letting your friends and neighbors know that only rain belongs down the drain!

To learn more about Philadelphia’s waterways and watersheds visit our watersheds page.