Tap Water to Get Annual Chlorine Flush

In what has become a spring ritual, authorities will temporarily resume the use of chlorine next week to treat drinking water used in the District and parts of Virginia, federal authorities announced yesterday.

For about a month, there might be a slight chlorine taste and smell to tap water, officials said. But the water will remain safe to drink, said the Washington Aqueduct, the arm of the U.S. Army Corps of Engineers that processes the city's water.

Aqueduct water, drawn from the Potomac River, also goes to Arlington County, Falls Church and parts of Fairfax County served by the Falls Church system.

From April 6 to May 4, the chlorine will replace chloramine, the disinfecting chemical used most of the year, the aqueduct said in its announcement.

Chloramines, combinations of chlorine and ammonia, are less reactive than chlorine and produce lower concentrations of the undesirable chemical byproducts of chlorine disinfection.

Those byproducts are formed when chlorine reacts with natural material in the water, such as leaves, grass and algae. The byproducts are suspected of causing cancer, the aqueduct said.

In its announcement, the aqueduct emphasized that the water will continue to meet federal health standards while being treated with chlorine.

According to the aqueduct, concerns about a possible link between the disinfection byproducts and miscarriages "have not been confirmed by scientific studies." But the announcement said women who are worried might want to use other water for drinking during the time of chlorine use.

As a matter of routine, the aqueduct said, people with special health concerns should consult their health care providers on the use of tap water.

Water customers who routinely take special precautions to remove chloramine from tap water should take the same precautions with chlorine, the aqueduct said. Those customers would include operators of dialysis centers and other medical facilities and aquarium owners. The aqueduct said most methods for removing chloramine from tap water are effective in removing chlorine.

Any noticeable chlorine taste might be reduced by refrigerating the water overnight, the aqueduct said. It said any discoloration should be temporary and eliminated by letting the cold water run.

Chloramine has been used by the aqueduct since 2000 after the Environmental Protection Agency tightened the limits on concentrations of chlorine byproducts. But a chlorine flush has been carried out each spring in recent years to kill microorganisms and help clean the network of distribution pipes.