People in Flint still should be drinking only filtered water or, in the case of pregnant women and children under six, bottled water.
But officials say there are hopeful signs that phosphates are re-coating the Flint water system's damaged pipes, and may be lowering the amount of lead getting into the water.
U.S. EPA On-site Coordinator Mark Durno says phosphate levels in the city's water mains are rising.
"We were putting about 4 mg (per liter) dosage at the water plant and we were seeing 1 to 2 mg (in the mains) over the course of December and January," Durno says. "Now we're seeing over 3. Which means the phosphate has really consumed itself within the mains. Now we're looking for the phosphate to work its magic in the service lines and in the interior residential plumbing."
Durno acknowledges that the mains and service lines on the outskirts of the system are probably not getting coated as much. That's because there are fewer customers there, so those lines are less used.
He says the EPA will likely recommend that Flint deliberately flush outlying pipes by opening hydrants and letting water flow through the pipes in large amounts.
In addition, people are being urged to run unfiltered water in their homes for up to five minutes a day, before turning the filter back on. That will start coating any lead pipes inside the homes with phosphates.
Durno says there's no estimate at this point when Flint's water will be safe to drink straight from the tap.
He says the damage done to the system was mostly likely greater than the damage done in Washington, D.C's system in 2001.
"Washington, D.C. took six months for those pipes to come back and get back to their pre-corrosion condition," says Durno. "We're about two and a half months into this, so from a timing standpoint it could be a little bit longer."
But Durno says he is confident that water filters are keeping people safe. The water filters are certified to remove 150 parts per billion of lead from water, but in many cases they are removing far more than that.
In one home, he says, "Our unfiltered sample came back at 4,000. Our filtered sample came back at 0.6."
Durno says he drinks filtered water from the Flint water system every day at his place of work.
Officials plan to release the results of new tests for lead in water in mid-April.
