About WSSC (Kids)


lab technician checking chemicalsThe Washington Suburban Sanitary Commission (WSSC) provides safe and reliable drinking water.  WSSC serves nearly 1.8 million customers in Prince George’s and Montgomery counties.  We also treat wastewater and return it as clean water back to our environment.

WSSC is one of the largest water and wastewater utility in the nation.  We have two water treatment plants.  We are also run six wastewater treatment plants.  We maintain over 5,400 miles of drinking water pipeline.  We also maintain over 5,300 miles of sewer pipeline.

Water Source

If you are WSSC customer, your drinking water comes from the Potomac and Patuxent rivers. WSSC created two reservoirs on the Patuxent.  These reservoirs are called Triadelphia and Rocky Gorge.

The Potomac River feeds the Little Seneca reservoir.  Little Seneca is used as an emergency water supply.  

The total amount of water that all three reservoirs can hold is 14 BILLION gallons! WSSC runs two water filtration plants. The Potomac River Filtration Plant gets its water directly from the Potomac.

The other plant is located next to the Patuxent in Prince George’s County.  The Patuxent Filtration Plant is fed by water from the Rocky Gorge reservoir. View an explanation of how WSSC treats our drinking water.

Wastewater Plants

worker putting in cables

What happens to the water you wash down the drain? Or what you flush down the toilet?

Wastewater in Prince George’s and Montgomery counties is sent to 7 different wastewater plants.  One is Blue Plain Wastewater Treatment Plant, operated by DC Water.  The other six plants are operated by WSSC.  The clean water is then returned to the environment. View an explanation of how this process is done.


WSSC was established in 1918. Wastewater from Montgomery and Prince George's counties were polluting rivers that flowed into Washington DC.  

worker attaching a pipeSo the leaders of Washington DC requested to the state of Maryland to clean this wastewater.  So Maryland established Washington Suburban Sanitary Commission.  WSSC then bought existing water and sewage systems within Prince George’s and Montgomery counties.  These systems were merged to create a larger, regional system.

The first reservoir, Triadelphia, was created by the construction of Brighton Dam on the Patuxent River in Brookeville. This dam was completed in 1943. The Patuxent River Filtration Plant was constructed near Laurel in Prince George's County in 1944. The T. Howard Duckett Dam and Rocky Gorge Reservoir were completed in 1952, bringing the water supply closer to the plant.

The Commission built the Potomac River Filtration Plant in Montgomery County to take and treat water from the Potomac River in 1961. In 1985, the Commission completed construction on Little Seneca Creek Dam and Reservoir as an emergency water supply.

gates open on damThe Growth of Water Mains in Prince George’s and Montgomery Counties

Since WSSC was founded in 1918, the number of people and homes in Prince George’s and Montgomery Counties have grown.  Here is an animated sequence showing the number of water mains that went into both counties.  With the construction of water mains, homes, schools and other buildings began to be built. 

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