Boil Water Advisory: What to Actually Do

A boil water advisory means your utility has reason to believe the water may be contaminated with disease-causing microorganisms — often after a main break, a loss of pressure, or a treatment problem. The instructions are simple, and following them exactly is what keeps you safe.

The core step: boil correctly

Per EPA emergency guidance, if you have tap water that is clear:

Bring the water to a rolling boil for at least one minute.
At altitudes above 5,000 feet, boil for three minutes.
Let it cool on its own — don’t add ice made from unboiled tap water.

Boiled (then cooled) water is safe for drinking, making ice, brushing teeth, washing produce, preparing food, and mixing infant formula. If the water is cloudy, filter it through a clean cloth or let it settle first, then boil.

If you can’t boil

If boiling isn’t possible, EPA guidance allows disinfecting clear water with unscented household chlorine bleach — a small, specific dose per gallon, mixed and left to stand. Follow the exact ratio in the EPA guidance rather than guessing, or use commercially bottled water.

The dangerous misconception

Here’s the part people get wrong: boiling does not remove chemical contaminants. The EPA is explicit that “boiling or disinfection will not destroy other contaminants, such as heavy metals, salts, and most other chemicals.” In fact, boiling can slightly concentrate something like lead as water evaporates.

So the type of advisory matters:

Microbial advisory (bacteria, parasites, loss of pressure): boiling works.
Chemical advisory (a spill, lead, nitrate, PFAS, “do not drink / do not boil”): do not boil — use bottled water and follow the utility’s specific instructions. A “do not use” or “do not boil” notice is a chemical situation, not a microbial one.

When in doubt, read exactly what your utility’s notice says, because the two situations call for opposite responses.

When the advisory is lifted

Once your utility clears the advisory, flush your plumbing: run cold taps for several minutes, flush and refill the water heater if advised, and discard ice made during the advisory. Then you’re back to normal.

To understand which contaminants boiling can and can’t address, browse our contaminant pages, and check your system’s track record with its Tap Grade.

Sources

US EPA — “Emergency Disinfection of Drinking Water” — https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water
US EPA — “Ground Water and Drinking Water” — https://www.epa.gov/ground-water-and-drinking-water
US EPA — “National Primary Drinking Water Regulations” — https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations