City officials said they will conduct the flushing at night in an attempt to minimize the inconvenience to water customers. The flushing is intended to improve water quality by cleaning out the supply lines, according to a news release.

Crews will begin work at 9 p.m. Sunday and flush large water supply lines until 6 a.m Monday. The effort will start with water mains leading from the Brown Water Treatment Plant on the city's north side and systematically move south through Dec. 1.

Workers will then begin flushing the smaller lines, targeting sections of the city's service area in parts of southern Durham. This work will be completed by mid-December.

Because of the holidays and anticipated cold weather in January and February, flushing elsewhere will be delayed until spring.

The first section of the city in which flushing will be done includes the Penrith Townhomes, where the lead poisoning of a child last spring was linked to tainted water in the apartment where the child's family had lived.

A city spokeswoman was emphatic that there is no relation between concerns about lead contamination and the upcoming flushing of the water lines.

"There is no connection," said Beverly Thompson, the city's director for public affairs. "This is a normal systemwide flushing. They do it every couple years."

Terry Rolan, director of Durham's Department of Water Management, said in the written statement that forcing water at a high velocity through underground pipes removes residue from the piping, which improves water quality.

While the flushing proceeds, there is the potential for air to become trapped in the lines or for the water pressure to drop slightly.

Tap water may also become slightly discolored. Running the tap for a few minutes should clear up the problem, but if the water continues to be cloudy or discolored, the city requests that its customers call Water and Sewer Maintenance at 560-4344.

Discolored water does not necessarily pose a health risk, the city release said, and crews will check chlorine residuals to ensure adequate disinfection levels.

However, customers are advised not to wash white clothing if water is discolored because of the potential for stains.