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Winter Weather and Water Main Breaks

Fact Sheet

Winter’s lower temperatures increase the chances of water main breaks in Prince George’s and Montgomery counties by about 60 percent compared to warmer months. Breaks can not only leave hundreds of people without service, they can also cause traffic problems.  That’s why WSSC takes winter preparations very seriously.  We have skilled teams, contractors on standby, and trucks, heavy equipment and the latest technology ready to roll.

Water Mains

  • Serving a 1,000-square-mile area, WSSC maintains more than 5,500 miles of water mains. That's enough pipe to stretch from Washington, D.C. to California and back!  And we’re replacing more than 35 miles of pipe each year.
  • WSSC's water mains range in size from 1 inch to 96 inches (8 feet) in diameter.
  • Of the 5,500+ miles of water mains in our distribution system, approximately 2,900 miles are cast iron pipe (16-inch diameter and less) constructed before 1977, and are responsible for 98 percent of the water main breaks.
  • Cast iron is a brittle material that is very sensitive to external pressure placed on the pipe.
  • Cast iron pipes were used from 1916 to 1976. Since 1977, WSSC has used ductile iron pipes.
  • Ductile iron pipes are stronger than cast iron, pre-lined with cement mortar and are not brittle.
  • The most common size for a water main is 8 inches, followed by 6, 12, 10 and 16 inches.

How Temperature Impacts Water Mains

  • A 10-degree change in the air or water temperature can dramatically increase stress on a pipe.
  • Water temperature below 40 degrees F can cause pipes to become more brittle.
    Air temperature at or below freezing causes the ground above a pipe to freeze - increasing external stress on a pipe.
  • Since the drop in water temperature lags behind air temperature changes, water main breaks may occur one to two days after a cold spell.

Other Factors That Contribute To Breaks

  • Material -- Most breaks occur in cast iron water mains.
  • Soil Erosion -- A previous pipeline break, excavation or nearby construction activity 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 diameter, the greater the risk of breakage.
  • 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.
Winter Weather Strategy

As colder temperatures settle into the region, they can also settle into our 5,000 miles of underground water mains - causing pipe breaks that can potentially leave hundreds of customers without service and impact area roadways. WSSC is ready to tackle winter weather water main breaks with:

  • A “24/7” rapid response center that handles emergency calls and quickly dispatches crews. For water or sewer emergencies, please call 1-800-828-6439 or (301) 206-4002;
  • More than 200 personnel trained to quickly respond to and repair water main breaks;
  • Teams strategically placed in both counties to respond to weekend and overnight emergencies;
  • Independent contractors available to supplement WSSC teams when necessary;
  • The latest technology used to pinpoint the exact locations of water main breaks;
  • Hundreds of pieces of heavy equipment to help teams excavate and repair breaks;
  • A Geographic Information System (GIS) computer program to help us better track and schedule water main maintenance and replacement activities; and
  • More than $372 million allocated over the next six years to replace nearly 300 miles of water mains.

It's important to protect your home plumbing pipes and inside water meter from freezing and bursting. Here are some tips to help winterize your home:

  • Repair broken windows, doors and walls and tightly close doors and windows to the outside;
  • Insulate outside walls;
  • Inquire at your local plumbing or hardware store about materials to insulate pipes and meters;
  • Seal all leaks in crawl spaces and basements. If your vents won't close, cover them from the inside with insulation, cardboard, plastic or newspaper;
  • Turn off the water to outside faucets, remove hoses and drain the pipes;
  • If a pipe freezes, completely open the cold water faucet nearest the frozen pipe. This will relieve the pressure and reduce the chance of breakage;
  • Use a hand-held dryer if you decide to thaw the pipe yourself; and
  • If you're not certain what to do, call a registered plumber for help.

View the links below to learn more about how winter weather impacts our pipes, and what you can do to protect your home plumbing pipes.

Current Maintenance Emergencies

View updated information on water and sewer line breaks or other problems affecting water and sewer services in the Prince George's and Montgomery county service areas.

Interactive Breaks and Leaks (Day by Day) Graph

View the latest graph that shows the relationship between water temperature and the number of water main breaks.

There is a relationship between water temperature and breaks.  A sudden temperature drop provides a kind of shock to the pipes.  Most of WSSC water comes from the Potomac River which feeds the WSSC Potomac Water Filtration Plan. When our air temperatures drop the water in the Potomac River drops too. It takes a day or two, but an increase in breaks and leaks soon follow. The river also brings the colder water from higher elevations to the west. 

The Patuxent River, and the two reservoirs formed behind Brighton and T. Howard Duckett dams, provide about 30% of the water for WSSC customers via the Patuxent Water Filtration Plant.  But the reservoirs are deeper than the Potomac River, and the temperatures don’t change as fast.  Therefore we have fewer breaks and leaks in areas served by the Patuxent Plant.


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