Atlantic City lifted its boil water warning just before 4 p.m. Sunday.
Mayor Marty Small held a news conference telling residents the water tested clear.
The Atlantic City Municipal Utilities Authority and several businesses offered clean water over the past two days, as the water system was flushed.
Residents were first told of the issue at a news conference Small streamed from his Facebook after 7 p.m.
The Atlantic City Municipal Utilities Authority first discovered the issue overnight.
A decision on the need to issue a water boiling order came at 4 p.m., after the state DEP came in and made the call, Small told BreakingAC.
The issue caused sludge to be recycled, which caused more iron to go into the water than could be filtered, causing cloudy water, Deputy ACMUA Director Clifford Keene explained.
"When the water is cloudy, there is a small potential contaminant can enter the system," he said, adding that the boil-water warning was being done out "an abundance of caution."
Residents were told to boil water before drinking it over the next couple of days.
The city's website at acnj.gov provided updates.
"We ask that you do not panic," said Harold Reeves of the Atlantic City Health Department said during Friday night's news conference. "There will be some debris in the water. Just let it run.
"We will be monitoring the situation to make sure you are in good hands," he added.
Emergency Services Director Scott Evans said they are working with the MUA to help in any way.
He also noted that, at the same time, fire hydrants will be flushed due the cold temperatures overnight Friday.
Drivers in those areas should be cautious of potential frozen water on the ground, Evans warned.
He said Public Works would be assisting to avoid issues.
