Washington Suburban Sanitary Commission (WSSC) provides safe drinking water and wastewater treatment for Montgomery and Prince George's Counties in Maryland. It was established on May 1, 1918, and is the eighth largest water and wastewater utility in the United States. The WSSC serves about 1.8 million people in an approximately 1,000-square-mile (2,600 km2) area. It owns and manages about 10,000 miles (16,000 km) of water and sewer mains.


A bi-county agency, WSSC has extensive regulatory functions. It promulgates and enforces the plumbing code for its jurisdiction as well as reviews and approves contract plans for extensions of water and sewer mains. The agency operates 3 reservoirs (plus shared access to a fourth reservoir), 2 drinking water filtration plants, and 6 wastewater treatment plants. It also collects wastewater which is treated by the Blue Plains plant (operated by DC WASA) in Washington, D.C.