In the wake of a deadly fire that incinerated Lahaina and destroyed 19 structures in the Upcountry hamlet of Kula, Maui residents in both areas are relying on bottled water, or water provided by the county, because of concerns the public water supply is contaminated.

Maui County officials have posted advisories saying residents should not drink or try to boil or filter local water because there is no way to guarantee its safety.

Officials ordered water sampling, with test results expected to come in late Thursday. Water and health officials will meet Friday to discuss them and determine next steps, said John Stufflebean, director of Maui County’s Department of Water Supply.

The fires’ intense heat likely melted plastics in the water system’s plumbing, possibly leaching contaminants including benzene, a human carcinogen, and volatile organic compounds, some of which are known or are suspected to cause cancer in people.

“When there’s fire happening, there’s smoke, there’s debris and some of the plastics in your water system can thermally decompose. This creates all sorts of pollutants,” said Andrew Whelton, professor of engineering at Purdue University who also directs the Center for Plumbing Safety.

Whelton provides expertise on restoring water systems to communities that have been devastated by wildfires in places like California, Oregon and Colorado.

Besides melted plastic, contaminants can also seep into water from gasoline, paints, household and industrial waste, burned electrical units and countless other sources.

Because of the risks, bottled water should be used for all drinking, brushing teeth, ice making and food preparation until further notice, according to Maui County.

People in Lahaina and Upper Kula are also advised to limit their use of hot water, not use hot tubs or swimming pools, wash their clothing in cold water and “use proper ventilation when using water indoors.”

If they do take showers, people should use only cold or lukewarm water and limit their exposure time since heat releases chemicals that can be inhaled or absorbed through the skin.

Hannah Faith Freed, a Kula mother of two, said the water situation is unnerving. The warnings have made her extremely wary of going anywhere near her faucets.

“I just don’t know enough about what’s in the water. Is it really safe? If I take a shower, I maybe stay in for two minutes,” Freed said.

She’s asked her family on the mainland to send her a solar shower so that she can heat up bottled water for bathing and avoid using local water.

“Our skin is our largest organ,” Freed said. “Why is cold or lukewarm OK and hot water not? How concerned do we need to be? How careful do we need to be?”

Kula resident Cheryl Brown said when the water came back on in her house a few days after the fire last week she assumed it was safe to use. She showered in it and ran it through her home water filtration system as a precaution.

When Brown learned of the water advisory, she immediately switched to bottled water for drinking. For personal hygiene, she uses dampened washcloths.

On Tuesday afternoon, Brown and Freed were both filling up jugs at a water “buffalo” tanker stationed at the base of Copp Road. They traded notes and information.

With information scarce, gathering with neighbors at buffalo tankers is proving to be a prime way to tap into the coconut wireless.

“It’s become our local watering hole,” Freed said.

Whelton said he thinks Maui County should instruct people not to use public water in Lahaina and Upper Kula at all until testing shows that it’s safe.

His message for state and county officials: “Show me the evidence that what you just told me to do has a basis in fact.”

The county is being extremely cautious and is basing its public guidance on standards set by the U.S. Environmental Protection Agency and the Hawaii Department of Health, Stufflebean said.

“You shouldn’t drink it. You shouldn’t use it for cooking. If you take a short, warm shower, that should be okay. You don’t want to get it hot because then the volatiles will come out. But again, we don’t know if there is anything in it and we won’t know until we get the test results back,” he said.

The guidance comes from years of experience with wildfires in California, Oregon, Washington and Colorado, Stufflebean added.

“We want to make absolutely sure that the water is clean and safe.”