Boil water notices

A notice, not a diagnosis

A boil water notice is a public-health advisory issued by your water utility, in coordination with the state or local health department, when tap water might be contaminated. The most common triggers are loss of system pressure (a water main break, a pump failure during a power outage), a positive sample for bacteria like E. coli, or a known intrusion event such as flooding around the treatment plant.

The CDC's published guidance is plain: when a notice is in effect, bring water to a rolling boil for one minute (three minutes above 6,500 ft) before using it for drinking, cooking, making ice, washing produce, or brushing teeth. After boiling, let it cool before use. That's the whole procedure.

What boiling actually does

Boiling kills bacteria, viruses, and parasites — the pathogens behind most waterborne illness. The one-minute rolling-boil threshold is conservative; the killing happens fast. The reason CDC adds two minutes above 6,500 ft is that water boils at a lower temperature at altitude, so the same pathogen exposure needs more time to reach the same inactivation.

Boiling does not remove chemical contaminants, heavy metals, or radiological hazards. If your notice is about a chemical spill, fuel leak, or industrial event, do not boil — switch to bottled water and follow the utility's specific guidance.

The hour before the notice arrived

Most boil water notices are issued after the contamination event has already happened. People drink the morning coffee. Kids brush their teeth before school. The dishwasher ran overnight. None of this is usually dangerous, but the right response depends on what you used the water for.

Drinking and brushing. Brief exposure to potentially contaminated water is usually not dangerous, but it can cause gastrointestinal symptoms (nausea, cramps, diarrhea) within a day or two. Watch for symptoms but don't panic. Symptoms that include bloody stool, high fever, severe dehydration, or last more than 24 hours warrant a doctor.

Dishes. Hand-washed dishes from before the notice can be re-sanitized: hot soapy wash, then a one-minute soak in a solution of one tablespoon unscented household bleach per gallon of cool water, then air-dry. Or simply run the dishwasher on a sanitize cycle — the high-heat dry on most modern machines exceeds the temperature needed to inactivate pathogens.

Ice and produce. Discard ice made during the notice period. Don't rinse fruit or vegetables with tap water until the notice lifts; use boiled-and-cooled or bottled water.

Infants, immunocompromised, and pets

Infants under one year. Formula should be made with boiled-then-cooled water or bottled water during a notice. Breastfeeding doesn't change. Boiled-and-cooled water is also the right call for sippy cups and bottles.

Immunocompromised household members. Cancer treatment, transplant recovery, HIV with low CD4, or other immune-suppressing conditions warrant extra caution. Use bottled water for drinking and brushing throughout the notice, not just the boiled-cooled standard.

Pets. If you wouldn't drink it, your dog or cat shouldn't either. Boil their water too, or use bottled. Most pets tolerate brief exposure fine, but the symptoms look the same as in people and need the same response.

Hot tap water. The temperature in a residential water heater is well below the boiling threshold and doesn't inactivate pathogens. "Run it hot" is not a substitute for boiling.