Boil Water Notices Explained: What to Do When Tap Water Is Unsafe

A boil water notice is issued by a health authority or utility when there is reason to believe that the public water supply is microbiologically unsafe. Common triggers include positive tests for E. coli, total coliforms or Enterococci, broken mains that allowed contamination, flooding, or treatment plant failures.

How long should you boil water?

Bring water to a rolling boil for at least three minutes. Let it cool covered, then store in a clean sealed bottle or pitcher. Refrigerated boiled water keeps for about 24 hours.

What the notice applies to

• Drinking and making beverages
• Cooking, washing fruit and vegetables
• Brushing teeth
• Preparing infant formula

Bathing and handwashing are usually fine. People with open wounds or weakened immune systems should take extra care.

Do household filters help?

Standard activated carbon pitcher filters do NOT reliably remove bacteria. During a boil notice, only certified hollow-fiber ultrafilters (pore size below 0.1 micron) or reverse osmosis systems with proper post-treatment are dependable. Look for NSF/ANSI 53 or P231 certification for microbiological reduction.

When is the notice lifted?

Only when the utility officially announces it. Check Aqualert for live alerts and all-clear notices in your region.

Be prepared

Keep at least 6 liters of bottled water per person at home. That covers two to three days of essential use if a fresh notice is issued.