The morning routine for most New Orleanians proceeded as usual Friday. As they brushed their teeth, took showers and made coffee, they had no idea that pressure in the city’s water system had dropped to potentially unsafe levels hours before, meaning the water across the east bank of Orleans Parish might be contaminated.

Sewerage & Water Board officials didn’t put out their first advisory until 10 a.m., seven hours after the initial problem at the agency’s Carrollton water treatment plant and two hours after data gathered from pumping stations across the city showed the pressure in the pipes had fallen to potentially unsafe levels.

City and S&WB officials described the advisory as a precautionary one, noting that the pressure drop was relatively short and the system is highly chlorinated to prevent contamination, but they urged residents to boil tap water for a full minute before using it to drink, bathe, shower, brush teeth or prepare food until test results come back from the state’s Department of Health and Hospitals. The results aren’t expected until Saturday afternoon.

It’s the latest in a series of pressure drops in the city’s water system over the years that have drawn criticism as much for what they say about the water infrastructure as for the lengthy periods that sometimes elapse before any public warning is issued.

Sarah McLaughlin, communications director for Mayor Mitch Landrieu, said repairs and upgrades to the water system would prevent future problems and the city is looking into the issue of how quickly advisories can be issued.

“S&WB is putting systems and protocols in place to ensure the pump station data from across the city is available more quickly so that the public can be informed as soon as possible,” McLaughlin said in an email.

The issue with the east bank’s system began about 2:55 a.m., when power surges were reported at the Carrollton treatment plant. That caused interruptions at the Claiborne and Panola pumping stations.

S&WB officials said the problem at the purification plant was caused by issues with the electricity it receives from Entergy. The power company released a statement Friday saying it had no record of any unusual event at the time of the incident.

Pressure remained above 20 pounds per square inch at the Carrollton plant, well above the level that triggers a boil-water advisory. But seven of the city’s 16 pump stations reported that their pressure dropped below the critical threshold, 15 psi, overnight, though the data were not gathered until 8 a.m. Those stations are at the Lakefront, Gentilly, the Almonaster-Michoud Industrial District, New Orleans East, the 9th Ward, Treme and the Central Business District.

Water in the system’s pipes is typically kept at about 68 psi. When it drops below 15 psi, the pressure is low enough that water from surrounding soil can seep into the system, possibly carrying with it bacteria that can cause diarrhea, nausea or other illnesses.

It was unclear why the recordings were not read until five hours after the incident.

“We’ll have more on that in the coming days and weeks,” Landrieu aide Ryan Berni said.

The state Department of Health and Hospitals was notified about the situation about 8:30 a.m., said John Ford, a spokesman for the department. The state agency typically works with local water systems to get a better sense of what happened in such situations.

“We’ll have to wait and see why the response time was the length it was, but if there is room for improvement we’ll certainly point it out and make those recommendations,” Ford said.

It takes at least 24 hours to test the water for contamination because the samples need time to incubate.

The S&WB has come in for repeated criticism for its handling of boil-water advisories. Notices often have come hours after the drop in pressure that caused concern.

Less than two months ago, the agency was blasted for waiting a day before issuing an advisory for English Turn and Lower Coast Algiers after a water main break caused pressure to drop below the critical threshold. Officials gave the all-clear two days after that notice was issued.

City Councilwoman Nadine Ramsey told S&WB officials at a recent public meeting that they should be quicker in providing information about such incidents.

The officials said at the time that they didn’t want to put out information until they had gathered more facts.

Other similar incidents have occurred over the years, including some caused by an aging power plant that is now being overhauled.

James Cullen, the chef at Press Station on Press Street, said his restaurant had been open for two hours Friday when the boil-water notice came through.

The lack of a quick notice, as well as a lack of information about exactly how restaurants and residents should respond to the advisory, proved to be headaches, Cullen said.

While the staff immediately worked to get into compliance with the advisory — substituting bottled water for tap, for example — lots of food and drinks already had been served. Some items, such as a five-gallon container of cold-brewed coffee prepared Friday morning, might go to waste.

“It’s a concern,” Cullen said. “You don’t ever want to get anybody sick; you don’t want to get yourself sick. And with customers, if they have a bad experience, they don’t want to come back.”

Improvements to the water system, including ongoing repairs to a century-old power plant that are expected to cost $150 million, could prevent problems in the future, S&WB Executive Director Cedric Grant said.

Those improvements would mean that power could be restored more quickly during a similar incident, he said. That work is expected to be completed in 2018.

The agency also is preparing to build a pair of water towers as part of a $50 million effort — known as a “water hammer” — that would push more water into the system to keep the pressure up when it starts to drop.

“Bringing these other systems on line will make us more resilient,” Grant said.