A precautionary boil-water advisory that was issued for part of upper Northwest Washington on Wednesday evening could remain in effect until Friday, officials of the District water and sewer authority said.

D.C. Water issued the advisory for areas west and southwest of Rock Creek Park after operations at a pumping station failed, said agency spokeswoman Nicole Condon.

The footprint of the affected area was reduced by 10 p.m. It’s mostly made up of a swath of Nebraska Avenue south of Military Road, extending west past Massachusetts Avenue NW.

The water outage means seven schools in Ward 3 will not serve breakfast Thursday and parents are encouraged to pack lunches for their students because limited lunch will be available at the schools. Bottled water will be available. The impacted schools include Hearst, Janney, Lafayette, Mann, Murch elementary schools, along with Deal Middle and Wilson High.

The agency advised customers who were experiencing low water pressure to boil their water for cooking and drinking because of the possibility that it was contaminated.

Areas of Northwest Washington included in the boil water order are shaded in blue. (D.C. Water and Sewer Authority)

“Within 24 to 48 hours, we’re hoping to lift [the advisory], based on our water-quality testing results,” Condon said.

She added that water service was restored to the area shortly before 7 p.m but that the advisory was still in effect.

A news release from the water agency said that customers who didn’t experience low water pressure and those who do not live in the affected area didn’t need to boil water.

As of 10 p.m., Condon said about 1,000 homes and businesses were still affected.

Customers who had low water pressure were advised to bring water to a rolling boil for one minute, allow the water to cool before using it and store the cooled water in a clean container with a cover. The failure at the Fort Reno pumping station Wednesday was caused by a switch gear failure, Condon said.