Most communities still boiling their water because of last week's water main break will likely be able to stop Sunday, though part of Farmington Hills is expected to remain under a boil water advisory until Monday.

A malfunctioning valve caused a drop in water pressure for a couple hours Friday night in northwest Farmington Hills, north of I-696, according to a notice posted Saturday on Oakland County's website.

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Because of the pressure drop, officials have to re-start the two-round testing process to determine whether water is safe for drinking, said Amanda Abukhader, spokeswoman for the Great Lakes Water Authority, which provides water and sewer services to communities in southeast Michigan.

The good news? The first round of tests for the other communities still under an advisory came back clear. They are Commerce Township, Orchard Lake, Walled Lake, West Bloomfield, Wixom, Novi (the area bordered by 14 Mile, Eight Mile, Napier and Haggerty), and the portion of northern Farmington Hills that did not experience Friday's drop in water pressure.

Abukhader said those areas will likely be able to stop boiling their water Sunday, pending good results of the second tests.

The advisory was lifted last week for other impacted communities.

The break Monday evening in the water main on 14 Mile Road between Farmington and Drake roads impacted 12 communities in Oakland County. A new section of pipe was brought in and repairs made on Wednesday.

Contact staff writer Ann Zaniewski at 313-222-6594 or azaniewski@freepress.com. Follow her on Twitter: @AnnZaniewski.