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A water main break leaves hundreds of people without service. So we take them seriously - especially in cold weather.

When cold weather arrives, the chance of water main breaks jumps by about 60% compared to warmer months. So we take winter preparations very seriously. WSSC Water has teams of skilled workers, trucks and heavy equipment standing by and ready to roll if a break happens.

When a water main breaks

How Temperature Impacts Water Mains

A sudden temperature drop causes a kind of shock to pipelines. Even a 10-degree change in the air or water temperature can dramatically increase stress on a pipe. Above-ground pipes can freeze when the air temperature hits freezing or below, and water temperatures below 40 degrees Fahrenheit can make pipes, including underground pipes, more brittle.

WSSC Water gets most of its water from the Potomac River, which feeds the Potomac Water Filtration Plant. When the air temperature drops, the Potomac's temperature drops too, bringing colder water into the system. It takes a day or two, but an increase in breaks and leaks soon follows. In contrast, water from the reservoirs formed by the Brighton Dam and the T. Howard Duckett Dam does not change temperature as quickly, because the reservoirs are deeper than the Potomac. That means fewer breaks and leaks in areas served by the Patuxent plant.

View our Interactive Water Main Breaks and Leaks Chart

Other Factors That Contribute To Breaks

  • Material: Of the almost-6,000 miles of water mains in our distribution system, approximately 2,900 miles are cast iron pipe (16-inch diameter and less), which were installed from 1916 to 1976. These pipes are prone to breaks because cast iron is a brittle material that is very sensitive to external pressure.
  • Soil Erosion: A previous pipeline break, excavation, or nearby construction often erodes soil around water mains, which can cause breaks.
  • Corrosion: Older pipes are not cement-lined and corrode inside and outside, increasing the chances of a break.
  • Pipe Diameter: The smaller the pipe’s diameter, the greater the risk that it will break.
  • Age: The break rate for pipes increases after 60 years. Age alone, however, cannot always be used as an indicator of failure. Some pipes installed in the early 1900s have never broken.

Facts about water mains

  • Serving a 1,000-square-mile area, WSSC Water maintains almost 6,000 miles of water mains - enough pipe to reach from Washington, D.C. to California and back.
  • We replace more pipe each year.
  • Since 2016, WSSC Water has installed zinc-coated ductile iron with V-Bio® Enhanced Polyethylene Encasement pipes, which are stronger than cast iron, are pre-lined with cement mortar and are not brittle.
  • The water mains range in size from 1 inch to 8 feet in diameter.
    Last Modified: January 5, 2023, 3:47 pm EST