Winter Weather
and
Water Main Breaks

In preparing for colder temperatures in the Washington, D.C. metropolitan area, the Washington Suburban Sanitary Commission (WSSC) is leaving nothing to chance. That's because as temperatures drop, the chance of water main breaks increases about 60 percent in Montgomery and Prince George's counties compared to warmer months. One water main break has the potential of leaving hundreds of customers without service. And because many of the mains are located under or near major roadways, a break can "dampen" the commute for thousands of motorists. With skilled teams, contractors on standby, and trucks, heavy equipment and the latest technology ready to roll, WSSC is prepared for winter weather.

WATER MAINS

• Serving a 1,000-square-mile area, WSSC maintains more than 5,000 miles of water mains with approximately 65 miles of new water main being constructed each year. That's enough pipe to stretch from Washington, D.C. to California and back!
• WSSC's water mains range in size from 1 inch to 120 inches (10 feet) in diameter.
• Of the 5,000+ 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.

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