Water mains are pipes that carry drinking water to people's homes and businesses. The Water Division of the Department of Public Works is responsible for the maintenance of these pipes.  Residents are notified by letter in advance of any scheduled water main work in their neighborhood.

Why clean water mains?
Cleaning and lining drinking water mains can prolong the life span of the pipe for less than the cost of replacing the pipe and with fewer service disruptions to residents. Instead of completely replacing the water main, it is possible to rehabilitate the pipe if it is in good condition. Corrosion deposits, known as tubercles, build up naturally over time in unlined iron water main pipes. The build-up does not normally affect the quality of the water, but it does reduce the effective diameter of the pipes, which decreases the capacity of the pipes. The buildup can also affect the pressure in the pipes.

A trenchless pipe rehabilitation method called Mechanical Cleaning and Cement-Mortar Lining is used. Trenchless methods involve only opening holes in the road at the ends of the pipe segment, instead of cutting the road open along the entire length of the water main. Trenchless methods are less disruptive to traffic flow through the work area. 

• The pipes are taken out of service for cleaning by closing the valves at either end of the line.
• The pipes are then mechanically or hydraulically scraped to remove all corrosion products.
• Once the pipe is cleaned and the water is removed, a thin lining of cement mortar is applied to the inside of the pipe, which prevents the water from interacting with the iron pipe and forming tubercles.
• After the mortar cures, the pipe is inspected, tested, disinfected, and placed back in service.

During times of extreme weather fluctuation pipes, soil, and water expands and contracts at different rates which occasionally causes water main breaks. When there is a break, crews will shut off the water flow and this will  interrupt resident’s services as the repair is completed. Once water is back on, residents may want to run their water for a few minutes to ensure that the water is completely clear. Town residents’ water bills are not affected when a break occurs. If a water main break has happened in your area call the Department of Public Works immediately at (703) 255-6380. After regular business hours, call the Vienna Police non-emergency number at (703) 255-6366.

When a water main is out of service during the cleaning and lining process, temporary service lines are used to provide water to the affected area. These temporary lines are disinfected and tested just like regular water mains before being placed in service. Residents will experience only a short disruption of water service during the installation and removal of the temporary lines.

Temporary service lines and newly lined water mains must be flushed before putting them in service. Flushing is performed to make sure that all water lines are free from any debris that may have entered the system. While this results in some amount of lost water, the overall quantity is small and allows us to maintain a high water quality throughout the cleaning and lining process.  The water is dechlorinated before it is discharged to the storm sewer.