An Atlanta water system disruption caused problems for residents, schools and businesses for about 25 hours this week and could cost the local economy hundreds of millions of dollars.

A boil-water advisory forced some restaurants to shut down, schools to distribute bottled water and hand sanitizer, and residents to take precautions.

The water problems, which covered large swaths of Atlanta and parts of DeKalb County, began Monday. City workers performing routine maintenance at the Hemphill Water Treatment Plant caused a "process control alarm" to go off, which signaled the pumps to shut off, city officials said. The city lifted the advisory Tuesday afternoon after water samples were tested and found no contaminants.

But by then, the damage was done.

Kishia Powell, commissioner of Atlanta’s Department of Watershed Management, said the city is looking into how to prevent the issue from happening again. The department serves 1.2 million people each day, but officials didn’t know how many homes were impacted. The Hemphill plant produces up to 55 percent of the water produced for the city each day.

“We certainly understand the inconvenience and the disruption, but what is paramount to us is protecting the public’s safety,” Powell said, during a press conference Tuesday afternoon.

A study commissioned by the city found that a day without water in Atlanta has an economic impact of about $250 million, factoring in the effects on businesses and salaries, Powell said.

Boil-water advisories are an inconvenience to people who have to abruptly change their habits. The city warned people to brush their teeth with boiled water, throw out all ice made with tap water and use disposable plates, cups and utensils until the situation was remedied. But for businesses, such an advisory can also mean an interruption in daily operations — and taking a hit financially.

 Picture shows Atlanta Hemphill Water Treatment Plant in Atlanta on Tuesday, December 4, 2018.

HYOSUB SHIN / AJC

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HYOSUB SHIN / AJC

Multiple Atlanta restaurants closed as a result of the advisory, including hotspots like Starbucks, with multiple city locations, Krispy Kreme on Ponce de Leon Avenue and the downtown location of The Varsity. Ten Kroger stores were affected, and the grocery store brought in extra water.

The manager of Little Star Provisions, Nell Mayer, had to turn down about 20 customers looking for coffee Tuesday morning.

“In this day and age, any loss of business is very problematic,” Mayer said.

For some, the issue was a flashback to July 2017, when a power outage at the Hemphill High Service Pump Station triggered a temporary loss of pressure that also resulted in a boil water advisory. In that instance, the system was restored to normal operations in about 40 minutes, but Atlanta hospitals, homes and businesses were impacted for about a day. Samples confirmed no systemwide contamination had occurred.

In March, a massive water main break that flooded Buford Highway in DeKalb County instigated a boil water advisory for the area. Numerous healthcare facilities in the county temporarily closed, but that break did not affect APS or DeKalb residents who received water from Atlanta’s system.

This week, though, Atlanta Public Schools were impacted; about 80 of its sites, mostly schools, were under the boil-water advisory. That presented a logistical puzzle: Providing safe drinking water and lunch for thousands of students.

Schools remained open Tuesday, though they took precautions. The district distributed bottles of water and provided packaged, ready-to-eat meals that didn’t require cooking in kitchens.

KIPP Atlanta Collegiate Principal Chanika Perry made sure that the school dumped all its ice and stocked the salad bar with canned fruit Tuesday. The school stationed cases of bottled water on each of its three floors so students had ready access.

While the school managed, Perry was thrilled when she heard the city had lifted the boil-water advisory Tuesday afternoon.

“Amen,” she said. “We were worried [Monday] because, of course, our first thought is ‘uh-oh, we’re going to have to shut down the building.’”

APS began dropping off pallets of water bottles at 6 a.m. Tuesday at Drew Charter School. The district delivered enough water to serve the charter school’s 1,800 students, said Head of School Don Doran.

Drew had stocked up on hand sanitizer in anticipation of flu season, so students were able to keep their hands clean. Signs were posted near drinking fountains warning students not to use them.

The charter school emphasizes project-based learning based on “real-world” topics, and Doran found a silver lining to the unexpected problem: an opportunity to teach students how to “deal with potentially unclean water which a lot of the world deals with.”

At KIPP STRIVE Primary School, the water stopped for about 45 minutes at about 10:45 a.m. Monday. Toilets didn’t flush, faucets stopped flowing, and the drinking fountain went dry.

Principal Lakeesha Ramdhanie and her operations director taped up the water fountains so that none of the roughly 500 students would accidentally try to use them. The school sent out a flurry of messages alerting people to the problem.

“We went straight into communication mode so that our team members and staff knew exactly what was happening,” Ramdhanie said.

It served nachos for lunch, a meal that didn’t require using water.