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San Francisco is the only coastal city in California with a combined sewer system that collects and treats both wastewater and stormwater in the same network of pipes. That means the rain that runs off your roofs and streets gets treated at our plants just like the wastewater that goes down your drain.
San Francisco's hilly geography comes in handy too. Water flows through most of the sewers using gravity. This reduces the energy and maintenance costs associated with mechanical pumping. View our map to find out the general direction your wastewater flows. (Hint: It is either East or West)
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| One of the many brick sewers beneath San Francisco streets. |
Almost 1000 miles of sewer are beneath the City's roadways. If the sewer pipes were laid end-to-end it would span the distance between Portland, Oregon and San Diego, California!
Why do we need to treat stormwater?
Cleaning stormwater is just as important as cleaning wastewater because of the street pollutants that wash into the sewer system. Imagine all the motor oil, pesticides, metals, and other street litter that you see on the street. They all go into the sewer system when it rains.
You still need to be careful about products you dump down the drain or use in your garden though. These same harsh chemicals can still possibly harm the environment and your family's health. Click here for some non-toxic tips for home cleaning and gardening. Here is a fun example of what you can learn: Did you know that toothpaste can clean silver AND give you healthy teeth?
Wait a minute! Does the 80 million gallons treated every day include stormwater?
Good catch! It doesn't. San Francisco generates about 80 million gallons of wastewater a day on non-rainy days. When it rains, our wastewater system collects and treats up to 500 million gallons a day. That is a lot of wastewater and stormwater!
Get involved and learn how to “harvest” or capture rainwater in barrels. You’ll save money, conserve our drinking water supply and reduce the burden on our sewers. Find out more about our rainwater harvesting programs.
How do we capture and store all that rainwater?
Well, that brings us to our next topic. Next Step: Catch Basins and Storage Boxes
