Denver Water chemists this week will lower the acidity of the water delivered to 1.4 million residents, part of a push to reduce the lead contamination from old pipelines that afflicts millions of homes nationwide.

Starting Tuesday, utility crews will tweak the pH level of Denver’s water supply from 7.8 to 8.8, officials said. This slightly lower acidity, kicking in widely over the next few weeks, is meant to protect residents from the risk of elevated lead in drinking water that leaches from corroding lead service lines and household plumbing.

Raising the pH level won’t affect the taste or odor of drinking water, Denver Water officials said.

The adjustment is expected to minimize corrosion and ensure safe tap water while contractors over the next 15 years dig out and replace tens of thousands of lead pipelines that connect water utility main lines to homes.

An estimated 64,000 to 84,000 customer-owned lead pipelines must be replaced with copper lines, according to Denver Water’s latest estimate. Over the past four years, contractors have replaced about 5,000 lead pipelines, and utility officials said they’ll pick up the pace and remove 4,500 a year.

“Nothing is more important than protecting the health of our customers, especially children,” Denver Water chief executive Jim Lochhead said.

Denver’s lead reduction drive reflects persistent concerns about lead and other contamination of drinking water that were piqued by the discovery in 2015 of elevated lead levels for more than a year in Flint, Michigan.

An estimated 6 million lead pipes around the country connect homes to water mains. Then-candidate Donald Trump in 2016 pointed to this problem and, during a visit to Flint, called for “crystal-clear water.” Last year, Environmental Protection Agency officials proposed stronger oversight of lead in drinking water, as part of a national “war on lead,” but also a slower timetable for replacing lead pipes.

In the past, cities have relied mostly on the manipulation of water supply chemistry to try to slow lead pipe corrosion, rather than replacing old pipes.

Denver residents own the service lines that may contain lead. Denver Water contractors a few years ago began replacing these lines at no cost to homeowners.

In December, EPA and state health officials approved Denver’s plan, which also includes creating a public inventory of customer-owned lead lines and providing free water filters for those with lead lines.

Officials at the Colorado Department of Public Health and Environment in 2018 had ordered Denver to inject an anti-corrosive chemical called orthophosphate into water supplies by March 20, 2020, after conducting a two-year study that was completed in 2017.

Denver Water objected, saying orthophosphate could lead to health harm, environmental harm to reservoirs and the South Platte River Basin, and higher wastewater treatment costs. A dispute between state health officials, Denver Water, Aurora and others spilled into court.

State health officials now have signed off on Denver Water’s overall plan, including the pH adjustment to reduce the extent of lead leaching out of old pipelines, said John Putnam, the state’s environment programs chief.

“We believe it is going to be a net benefit for people, especially for those with lead-related issues,” Putnam said. “We want to make sure we’ve got eyes on it. Denver Water is going to be monitoring it closely and reporting to us on any changes they see.”

The water that Denver diverts from mountain streams and delivers through trans-basin pipelines is lead-free. The problem has been the service lines and plumbing inside homes.

No amount of lead in water is healthy, according to the U.S. Centers for Disease Control and Prevention. Even relatively low levels can hurt children — slowing growth, impairing hearing and digestion, shortening attention spans and stunting academic achievement.

Denver Water officials have known since 2012 or earlier about lead contamination caused by what the utility a few years ago estimated to be about 58,000 lead pipelines between water mains and homes.

In 2012, required tap-water tests in homes showed that lead levels exceeded a federal health “action level” limit of 15 parts per billion, set in the early 1990s under the Safe Drinking Water Act. State health department records showed that 13% of tap water samples taken that year contained lead at levels above the limit as high as 57 ppb.

Subsequent testing in homes showed elevated lead levels ranging from 7 ppb to 13 ppb, with the levels at some homes (fewer than 10%) above the 15 ppb limit.

Elsewhere, utilities have been delivering water to residents with pH levels above 8 on the pH scale. Among those supplying more than 50,000 people in Colorado, Westminster has maintained a pH of 8.5 to 8.6 for the past six years, Denver Water officials said.

The Massachusetts Water Resources Authority that delivers water to 3.1 million people in the Boston area adjusts its water to a pH of 9 to 9.5 — to reduce the potential that water will leach metal from household plumbing, Denver officials said. And San Francisco utilities serving 2.7 million customers adjust the pH of the water throughout the year from 7.8 to 9.9, averaging 9.4, depending on sources of the city’s water supply.

Denver Water officials said they’re working with irrigation and landscape experts to prevent any impacts on vegetation.

“There should not be any major impacts,” utility spokesman Travis Thompson said, because pH levels are reduced once water is exposed to air during irrigation. Soil filtration also would buffer impacts on plants.

“We’ll continue to work with the experts and other cities in this pH range to learn more,” Thompson said, “so we can appropriately communicate any best management practices to help mitigate any anticipated issues.”