Boil water notice: what it means and what to do.
A boil water notice (also called a boil water advisory) is a public warning from your water system telling you to bring tap water to a rolling boil for one minute before drinking, cooking, or brushing your teeth. It is issued when water may be contaminated — and stays in effect until testing confirms the water is safe.
What to do during a boil water notice
Boil first, then cool
Bring water to a rolling boil for at least 1 minute (3 minutes above 6,500 ft / 2,000 m), then let it cool. Boiling kills bacteria, viruses, and parasites. Or use bottled water.
Safe without boiling
Showering and bathing (avoid swallowing), hand-washing with soap, laundry, and running the dishwasher on a hot/sanitize cycle are all fine for most healthy adults.
Use boiled or bottled for
Drinking, making ice, brushing teeth, washing produce, preparing food, mixing baby formula, and filling pet bowls. When in doubt, boil it or use bottled.
Protect infants & vulnerable people
Use bottled or boiled-then-cooled water for infant formula. Sponge-bathe young children so they do not swallow water. Take extra care with anyone immunocompromised.
Why water systems issue boil water notices
Bacteria detected
A positive total coliform or E. coli sample under the Revised Total Coliform Rule (RTCR) can trigger a notice while the system re-samples and investigates.
Loss of pressure
A water main break, power outage, or pump failure can drop system pressure and let contaminants in — a precautionary boil notice follows until pressure and quality are confirmed.
Treatment disruption
A disinfection or filtration upset means the system can no longer guarantee pathogens are removed, so it advises boiling until treatment is verified back to normal.
Issuing the notice? It’s a Tier 1 public notification.
Under the federal Public Notification Rule (40 CFR § 141.202), an acute boil water advisory is a Tier 1 notice: it must reach customers within 24 hours, carry the EPA-mandated health-effects language, and — in many communities — be delivered in both English and Spanish.
1water is building an operator toolkit — a coliform-response wizard and a public notification generator with the verbatim Appendix B health-effects language (§ 141.205) — to draft the right notice the moment a sample comes back positive. Tell us your state →
Boil water notice — common questions
- U.S. CDC — Making Water Safe in an Emergency (boiling guidance).
- U.S. EPA — Revised Total Coliform Rule (RTCR), 40 CFR § 141 Subpart Y; and the Public Notification Rule, 40 CFR § 141 Subpart Q (§ 141.201–141.205).
Keep reading
Coliform bacteria in water: what a positive result means
Total coliform vs fecal coliform vs E. coli, what a positive test means, and how to fix coliform in well water.
Nitrate in drinking water: limits, risks & what to do
The 10 mg/L EPA limit, why nitrate is an acute risk to infants, where it comes from, how systems remove it, and the 24-hour notice an exceedance requires.
Arsenic in drinking water: limits, risks & removal
The 0.010 mg/L (10 ppb) EPA limit, why arsenic is a chronic cancer risk, where it comes from, how systems remove it, and the Tier 2 30-day notice an exceedance requires.
Compliance shouldn't wait for a crisis.
1water helps small and mid-size water systems stay ahead of coliform, lead, PFAS, and CCR requirements — self-serve, and priced for the small end.