The D.C. Water and Sewer Authority is conducting its annual program to flush water mains, a procedure designed to remove sediment and improve drinking 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 beginning Aug. 1:

* ANC 6B (work area in Southeast, bounded by E Street, 17th Street, L Street and 12th Street).

* ANC 4D (in Northwest, bounded by Farragut Street, New Hampshire Avenue, Allison Street and Illinois Avenue).

* ANC 2B (in Northwest, bounded by O Street, Connecticut Avenue, L Street and New Hampshire Avenue).

* ANC 4B (in Northwest, bounded by Missouri Avenue, 4th Street, Jefferson Street and Georgia Avenue).

For information, call the WASA Water Quality Office, 202-612-3440, 8 a.m. to

4 p.m. In an emergency, call WASA's 24-hour hotline,