Combined Sewer Overflow

Interactive Educational Simulation

Rainfall Intensity
Dry 0% Storm
No Rain
Sewage Flow Rate
Low 50% High
Normal Usage
System Status
Stormwater Runoff0%
Sewage Flow50%
Chamber Level14%
River Pollution0%
📊 Did You Know?
About 860 U.S. cities still use combined sewer systems, many built over 100 years ago.
LESSON 1 OF 6
What is a Combined Sewer?
Many older cities have combined sewers — a single underground pipe that carries BOTH sewage (from toilets/sinks) AND stormwater (rain runoff) to the treatment plant. Drag the rainfall slider to begin.
Stormwater (clean)
Raw Sewage
Mixed / Entering Treatment
CSO Overflow (untreated)