The Honolulu Board of Water Supply is asking O'ahu residents from Kahana Valley to Makapu'u to conserve water during a 24-hour period beginning at 6 p.m. Friday.

Water Supply crews will be closing a 30-inch main that provides water to Windward O'ahu reservoirs to make a water service connection, as part of the state Department of Transportation's North Kahana Stream bridge replacement project.

The connection is expected to take about 12 hours to complete, but a 24-hour conservation period is needed to allow the system to recover.

The Board of Water Supply says it will fill Windward reservoirs before the closure so customers will continue to have water service. However, the board will be limited in its ability to pump and refill the reservoirs while crews are making the connection.

Residents in affected areas are asked to use water sparingly from 6 p.m. Friday to 6 p.m. Saturday. Water should be used only for cooking, drinking and personal hygiene.