Virginia Tech researchers are sounding new alarms about lead in Chicago’s water.

Tests they performed this summer on the South Side show that about a third of the tested homes delivered water with more lead than would be allowed in bottled water, according to results announced Monday at Nat King Cole Park in the Chatham neighborhood.

But the tests also showed another disturbing trend: Lead levels in many homes got higher as the water ran for up to three minutes.

In fact, the study found that after three minutes of running water, Chicago has more lead on average than Flint, Mich., during its 2015 water crisis.

Three minutes “is about the longest we normally see consumers flush,” said Marc Edwards, who led the U.S. Water Study Research Team doing the tests for this study. “And after three minutes of flushing they were higher than in Flint during the height of the water crisis in 2015.”

For this reason, Edwards and Chicago water officials warn consumers to flush their water longer than three minutes before drinking the water. Running one tap can clear the water for the whole home.

“Like Edwards, the Chicago Department of Water Management continues to advise residents with lead service lines or fixtures to flush their water for five minutes every time their water has been stagnant for six hours or more,” Water Department spokeswoman Megan Vidis wrote in an email to WBEZ.

About 80% of Chicago homes — mostly those built before 1987— have lead service lines connected to their homes. Researchers suspect the reason lead levels rise after running the water for around three minutes is because that is when the water that has been sitting in lead service lines reaches the tap.

City complies with federal rules

This latest findings, showing a third of homes with high lead, echoes data researchers published last year about homes in suburban Cicero and Berwyn — as well as the city’s own voluntary 311 lead testing.

In response to the findings, Vidis noted the city of Chicago consistently meets “U.S. EPA standards for drinking water of 15 parts per billion.”

That refers to the U.S. Lead and Copper rule, which requires all municipalities to periodically check their water for lead. In Chicago, that means testing just the first liter from the tap in 50 homes every three years. The city passes that test if 90% of results have lead under 15 ppb, which is three times higher than is allowed in bottled water.

Edwards said this low bar is unacceptable, in part because his study and others indicate that the first liter out of the tap is often much lower in lead than the water that follows.

“Everyone knows the Lead and Copper rule is not sufficiently protective and this is just a loophole — some even call it the Chicago loophole,” Edwards said. “The first [liter] draw seems low whereas the normal water people drink tends to be higher. Maybe this loophole will be closed when the new Lead and Copper rules are announced.”

An update to the 1991 Lead and Copper rule has been in the works for years, and is expected to be released later this summer. In the meantime, Edwards said Chicago can do a lot to help protect consumers. In addition to urging consumers to filter or flush their water for five minutes before use, he says the city can improve the balance of chemicals, called corrosion control, it puts in the water to prevent lead from leaching out of the pipes.

“We know there’s more water [officials] could do to optimize corrosion control,” he said, noting that other municipalities, like Flint use different levels of a pipe-coating chemical called orthophosphate to keep lead levels down.

It should be noted that much of this would be unnecessary if Chicago removed its vast network of lead service lines that city code required builders to install for decades — long after many cities had stopped using them. While Mayor Lori Lightfoot was a candidate she spoke about the importance of removing the lead lines, but her administration has still not announced a plan to do so.

“The results are very clear,” said Edwards, who helped uncover the Flint water crisis. “There’s sustained high lead in the water, even with flushing. I think folks should be aware of this and take it seriously.”

The cost of flushing water lines

For those counting, if all 392,614 Chicago homes with lead lines flushed one faucet in the home twice a day for five minutes it would result in about 5.88 million gallons of flushed water per day at a daily cost to residents of about $46,524.

In order to avoid wasting all of that water, some recommend using it for things like washing dishes, washing clothes, watering plants and taking a shower. Lead in bathing water is not considered a significant health threat.

Monica Eng is a WBEZ reporter. Follow her on Twitter at @monicaeng.