Residents affected by the chemical leak into the Elk River were advised to use an interactive web map at westvirginiaamwater.com, to see if they were still under the do-not-use alert of if they could start to flush their home plumbing system, the Charleston Gazette reported.
The process will require at least 20 minutes of flushing faucets, state officials said at a news conference Monday afternoon.
State officials warned customers not to begin the process until their zone's ban is lifted so the water system wouldn't be overloaded. If customers jump the gun before their area is coded on the online map, the recovery time will be extended, Jeff McIntyre, president of West Virginia American Water Co., said.
State schools chief Jim Phares said he was optimistic classes in Kanawha and Putnam counties could reopen Tuesday while the situation in Boone and Lincoln counties were being assessed.
Fourteen people were hospitalized with non-life-threatening symptoms that could be related to the chemical leak, officials said.
An estimated 7,500 gallons of the industrial chemical 4-methylcyclohexane methanol, used in cleaning coal, leaked from a Freedom Industries Inc. storage tank into the Elk River Thursday.
Since then, residents -- about 300,000 -- in parts of nine counties were advised not to use their tap water for anything except to flush a toilet.
Officials said more than 90 percent of tests indicated MCHM levels were now "well below the health risk level."
However, McIntyre couldn't say when the water would be usable.
"It's hard to predict because it depends on the behavior of the people. If people don't follow the instructions ... it will go longer," he said. "It could still be days before we have the entire system cleared. It's a very large, complex system."
U.S. Rep. Nick Rahall, whose district represents some of the affected counties, told the Gazette it was too soon to know whether any legislative changes would be made in Congress.
"My committee ... will be exercising our oversight authority, but in due time," said Rahall, the ranking Democrat on the House Transportation and Infrastructure Committee. "We want to look at what happened, how we can keep it from happening again and if, God forbid, it were to happen again, how can our response be better than it was this time?"
Government officials said Sunday chemical levels in the water dropped considerably during the weekend.
West Virginia Health and Human Resources Secretary Karen Bowling said more than 1,000 people called the state Poison Center about exposure concerns.
She said more than 60 animal exposures were also reported.
President Obama signed an emergency declaration for the nine counties Friday. The U.S. Department of Homeland Security sent 16 semitrailers loaded with bottled water to supplement the water company's truckloads.
Schools, day care centers, restaurants and bars were closed Monday.