St. Petersburg officials turn off water after main breaks during Milton landfall. Here are the health risks

Residents of St. Petersburg -- on Florida's central-west coast -- were temporarily left without clean drinking water after a water main break occurred during Hurricane Milton.

City officials said the break caused them to shut off potable water services at 12 a.m. ET on Thursday until repairs could be made.

"Residents and businesses should prepare for this temporary shutdown, which is expected to last until the necessary repairs can be completed," the city said in a release.

"Repairs to the water line will begin once it is safe for crews to be outside. Affected areas may already be experiencing low water pressure or service interruptions," the release continued.

By Thursday afternoon, officials said potable water service was back but that pressure may be low.

Additionally, officials said a helicopter from the Sheriff's Office in Pinellas County, where St. Petersburg is located, was assisting in searching for water main leaks.

Typically, water distribution systems are kept under enough pressure that, even when there are cracks, dirty water and contaminants are unable to get in. However, when a water main breaks, system pressure drops and pathogens are allowed to seep in.

"When water main breaks, we can see the obvious water coming out, and we think, 'Oh, we're losing water.' But what's happening in other areas of the system is the pressure is going down," Dr. Sandra McLellan, a distinguished professor at the University of Wisconsin-Milwaukee's School of Freshwater Sciences, told ABC News.

"What is in the soils can seep into the pipes. … If there's a water main break and there's a lot of flooding or a lot of rainwater, then all of that sewage that's kind of sitting around these pipes and in the soil can seep into our drinking water systems," she continued.

Some of the contaminants may be visible to the naked eye and just lead to discoloration or cloudy water. Other containments may not visible and lead to serious illnesses including E. coli or norovirus.

McLellan said people may not realize their drinking water is contaminated until they experience symptoms of illness.

"There's no real way to easily test for pathogens in the water because they're kind of at low levels," she said. "So it isn't that everybody's going to get sick, but, if 100 people drink the water, chances are one or two people may be drinking a part of the water that contains those pathogens."

Dr. Norman Beatty, an assistant professor of medicine at the University of Florida College of Medicine and an infectious disease physician, told ABC News that ingesting bacteria found in storm surge waters can lead to diarrheal illnesses, but can progress to sepsis in some and lead to hospitalization."

The city issued a boil water notice for water used for drinking, cooking and brushing teeth and said it will remain in place as repairs continue.

Beatty recommends using bottled water until the water is drinkable or boiling water.

"When boiling water, start the timer once you reach a rolling boil and after one minute, let the water cool naturally. If water is cloudy, let is settle and then filter through a clean coffee filter paper or clean cloth," he said.

McLellan said after a main break, crews will dig up the street, fix the pipes and restore pressure. She added that after pressure is restored, one flushing of the pipes should restore clean drinking water.

If people are worried about their water supply, she recommended they use a pitcher with a home water filter before drinking tap water.

"I think people think, 'Oh, if my water's off, of course there's a problem. But if my water's on, the water will be safe,'" she said. "But we really have to remember, in areas where there's hurricanes, there's certainly damage that could happen, so it's better to be on the safe side."

On Wednesday evening, St. Petersburg officials also turned off power to two sewer treatment plants in the northeast and southwest part of the to protect employees and the facilities from potential storm surges.

As of Thursday morning, sewer services were back online, and city crews were out inspecting and re-energizing both plants.

Hurricane Milton made landfall on Florida's west coast as a Category 3 hurricane Wednesday night.

Gov. Ron DeSantis said Thursday morning that the hurricane "thankfully" spared the state from "the worst-case scenario" but that flooding Is expected to continue over the next several days.