A boil water advisory is in effect for the entire village of Upper Nyack and parts of Valley Cottage after a problem with oxygen levels forced a local reservoir to shut down.
Low oxygen levels in the water at the Lake Deforest Reservoir forced the treatment plant to shut down on Monday.
United Water is now asking customers to boil water for one minute before drinking or brushing their teeth.
United Water officials say the water is safe for showering and washing cloths. The advisory is affecting nearly 800 people.