PROVIDENCE — Five years ago, when Providence Water was grappling with a lead problem, the Rhode Island Department of Health required the utility to create an expert advisory panel to help it address the public-health concern.

Since 2007 Providence Water, which supplies about 60 percent of Rhode Island with its drinking water, has exceeded Environmental Protection Agency (EPA) Lead and Copper Rule action levels 12 out of a possible 21 times. The EPA requires utilities to test their drinking water once during two annual semesters: January through June, and July through December.

Progress is steadily being made — for instance, Providence Water has met the standard four out of the past five semesters — but improving, protecting and maintaining water quality is a complicated business. It requires a meticulous attention to details.

“You don’t want to ignore the possibility that a small change could take you backwards somewhere else,” said Stephen Estes-Smargiassi, director of planning and sustainability at the Massachusetts Water Resources Authority. “You need to understand changing one thing can change a lot of other things. The last little bit of improvement is difficult. Improving the situation 80 percent or 90 percent is the easy part. That next step is a lot harder.”

Marc Edwards, a civil engineering/environmental engineer at Virginia Tech who helped bring the Flint, Mich., water tragedy into focus, listed some of the problems that could arise should the chemical makeup in a water distribution system not be properly calibrated: red, rusty water; water main breaks; growth of harmful bacteria; bad-tasting water; creation of disinfection byproducts.

“There’s great potential for something to go wrong,” he said. “It makes sense to proceed with caution.”

Both Edwards and Estes-Smargiassi are members of Providence Water’s six-person expert advisory panel. The other members are Abigail Cantor, a chemical engineer specializing in water-quality investigations and founder of Process Research Solutions LLC; Daniel Giammar, professor of environmental engineering at Washington University in St. Louis; Michael Schock of the EPA’s National Risk Management Research Laboratory; and Anne Sandvig, a senior associate at The Cadmus Group Inc.

Some of the consultants were paid a one-time stipend: Edwards, $57,721; Cantor, $23,799; Sandvig, $8,640; Giammar, $7,362. As federal and state government employees, neither Schock nor Estes-Smargiassi was compensated.

Five of the panel members were in Providence on Nov. 6 visiting with Providence Water general manager Ricky Caruolo, a 24-year veteran of the utility who took over as its top official in 2014, deputy general manager Peter Pallozzi, and executive engineer Gregg Giasson. The five outside experts, plus Caruolo and Giasson, met with ecoRI News that morning at Providence Water’s new headquarters on Dupont Drive. Sandvig was the only consultant not present.

The 30-minute conversation focused largely on the delicate balance required to keep a vital resource drinkable. The panel and staff participate in three to four conference calls annually, and they regularly share information. They may not agree on every point, opinion or suggestion, but that’s part of addressing a complex situation.

When the systems of lead pipes that run under older cities and towns, such as Providence and Cranston, were first installed, many people didn’t understand the dangers of lead poisoning. As a result, lead remains the primary connection for water running to older homes. The fix is complicated, and expensive.

This past summer, Caruolo told ecoRI News that, “We have a problem and we’re not going to hide it. Our priority is to make sure our end users are getting the best possible water. We’re looking into everything that we can do to keep our water quality high.”

On Nov. 6, Caruolo said maintaining product quality includes embracing the recommendations of six people who live outside of Rhode Island.

“The expert panel wasn’t created as some short-term solution,” he said. “They’ve made a commitment to us and we’ve made a commitment to them. We take their input seriously.”

Providence Water isn’t the only utility battling lead. Since 2013, about 1,400 water systems have reported excessive lead levels of more than 15 parts per billion at least once, according to the EPA. More than 18 million Americans got their drinking water from systems with lead violations in 2015, according to the Natural Resources Defense Council.

The source for Providence Water is the 37-billion-gallon Scituate Reservoir, and the water is delivered through some 1,000 miles of mains. The water at that point is lead-free. The problem starts with buried service lines, from the public main to the curb and from the curb to homes and businesses. Many of those service lines, both public and private, contain lead.

Antiquated infrastructure and hidden plumbing are the main culprits, but lead in drinking water is a multilevel problem that is further camouflaged by the fact many customers take the inexpensive product for granted.

Some 13,000 homes — about 17 percent of Providence Water’s 75,000 retail customers — are still serviced by utility-owned pipes made of lead that connect the public water main to private property. Another 25,000 or so private-side lead service lines remain in use within the utility’s service area. The cost to replace a lead service line is about $2,000 to $3,000 — a ballpark cost of about $95 million to replace the 38,000 or so lead service lines within Providence Water’s retail district. That estimated cost doesn’t include replacing lead soldering, fixtures and other sources hidden in homes.

Caruolo has estimated that it would costs hundreds of millions to remove all lead, both public and private, from the utility’s water system.

Since 2012, Providence Water has raised the pH of its water to initiate reactions that minimize lead corrosion. When water interacts with buildup inside pipes, it results in the increased or decreased leaching of lead. However, this is just one of the many possible responses that need to be considered.

Caruolo said the utility needs to project how changes made today will impact the system years from now. Edwards noted that utilities also needs to anticipate stricter water-quality regulations.

Cantor described the work involved as trying to steer an old ship. “There are many factors that are out of our control,” she said. “Water goes into pipes buried underground that have varying degrees of biofilm buildup and complex accumulations.”

Giammar noted that “every water system is unique” and there is no one way to protect, maintain or restore a system.