The D.C. Water and Sewer Authority is conducting its annual program to flush water mains throughout the city, a procedure designed to remove sediment and improve water quality.

From 10 p.m. to 6:30 a.m. Sunday through Thursday, WASA crews are opening fire hydrants in designated neighborhoods and flushing water.

The water supply to customers is not shut off during the flushing.

Customers might notice some water discoloration early in the morning. If that happens, WASA recommends that residents open the cold water tap and allow the water to flow slowly until it is clear.

Customers should not run hot water or do laundry during the flushing. If the hot water becomes discolored, WASA recommends flushing the hot water tank by opening the valve at the bottom of the tank.

The flushing program will continue through November.

These neighborhoods, with boundary streets, are scheduled for flushing the week starting Sept. 5:

* ANC 5C (work area bounded by Florida Avenue NE, Fourth Street NE, K Street NE and North Capitol Street NE).

* ANC 4C (bounded by Missouri Avenue NW, Fourth Street NE, Jefferson Street NW and Georgia Avenue NW).

* ANC 2A (work area in Northwest, bounded by Pennsylvania Avenue, 19th Street, E Street and New Hampshire Avenue).

* ANC 4B (work area in Northwest, bounded by Sheridan Street, Third Place, Missouri Avenue and Seventh Street).

For information, call the WASA Water Quality Office, 202-612-3440, 8 a.m.- 4 p.m. In an emergency, call WASA's 24-hour hotline, 202-612-3400.