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 Sunday, according to information provided by WASA:

* ANC 3D (work area in Northwest, bounded by Arizona Avenue, Chain Bridge Road and Potomac Avenue).

* ANC 2A (work area in Northwest, bounded by K Street, 24th Street, E Street and 27th Street.

* ANC 2E (work area in Northwest, bounded by Volta Place, 33rd Street, M Street and 37th Street).

* ANC 2A (work area in Northwest, bounded by G Street, 17th Street, Constitution Avenue and 23rd Street).

* ANC 2F (work area in Northwest, bounded by I Street, 10th Street, Constitution Avenue and 15th Street).

* ANC 2E (work area in Northwest, bounded by Q Street, 31st Street, M Street and 33rd Street).

* ANC 2E (work area in Northwest, bounded by Q Street, 29th Street, M Street and 31st Street).

* ANC 3D (work area in Northwest, bounded by Ashby Street, Hoban Road, Salem Lane and Canal Road).

* ANC 3D (work area in Northwest, bounded by Reservoir Road, 44th Street, P Street and Canal Road).

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.