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Boil water advisory: what it means and what to do

Live status: the state advisory lists we read

We read each of these state agencies' own advisory lists on an hourly cycle, and publish what the list said with the time we last read it.

Check a ZIP code

Enter a ZIP code and we will show you the water systems we hold for it, and what the state agency's list said about each one when we last read it.

Check a ZIP code on its own page

What a boil water advisory means

CDC puts it in one line: a boil water advisory tells you to boil your tap water before using it, because boiling kills germs. Everything else on this page follows from that one instruction.

New York State's health department lists what typically leads to one: loss of pressure in the distribution system, loss of disinfection, water line breaks, treatment disruptions, power outages and floods.

The thing to hold on to is that this is a notice about germs rather than about chemistry. That distinction decides how you should respond, and it is why the next section exists.

The three kinds of drinking water advisory

CDC groups drinking water advisories into three, and they are not interchangeable. Read which one your own notice is before acting on anything below, because the correct response to the second and third is the opposite of the correct response to the first.

  • Boil water

    Boil your tap water before using it. Boiling kills germs, which is the hazard this advisory covers.

  • Do not drink

    Use commercially bottled water for drinking and cooking, because swallowing chemicals or toxins in the water could make you sick. Boiling does not help here — EPA states that boiling or disinfection will not destroy other contaminants, such as heavy metals, salts, and most other chemicals.

  • Do not use

    Use commercially bottled water for all purposes, because swallowing, touching or having other contact with the water could be dangerous. CDC describes this as the rare one.

Why boiling is the answer to the first of those three kinds and not to the other two: what boiling kills, and what it does not remove.

How to boil water so it is safe to use

Four steps, and the first two carry the numbers that matter — CDC and EPA agree on the boil itself, and differ only on the altitude at which it gets longer.

  • Bring it to a full rolling boil for 1 minute

    CDC and EPA both give one minute at a full rolling boil. It is the figure the rest of this section is built on.

  • Above about 5,000 feet, boil for 3 minutes

    The two federal agencies set the trigger differently: EPA says three minutes at altitudes above 5,000 feet (1,000 meters), CDC says three minutes at elevations above 6,500 feet. We publish the more protective of the two, and give you both so you can see the range.

  • Let it cool before you use it

    New York State's health department notes that water may take 30 minutes to cool, so plan ahead rather than waiting on a kettle you need immediately.

  • Follow your own utility's notice where it asks for more

    Some local advisories specify a longer boil than the federal one-minute rule. The notice issued for your own water system is the one to follow.

A home filter does not replace boiling

CDC's instruction is one sentence: boil your tap water even if you filter it. New York State's health department answers the same question with a single word — "No!" — and Louisiana explains why: most kitchen and other household water filters do not remove bacteria or viruses. Florida agrees.

That is why you will not find a filter recommendation anywhere on these pages. A notice of this kind is about germs, and the equipment on a kitchen counter was mostly not built to remove them.

How to find out whether an advisory applies to your address

The notice issued for your own water system is the authoritative answer for your address, and it is where to start.

Read it for two things. First, which of the three advisory types it is, because that changes the answer to almost every question on these pages. Second, whether your system is asking for something different from the general guidance: some notices specify a longer boil than the one minute CDC and EPA give, and where they do, the notice wins.

It is also the only honest answer to how long you will be doing this. New York State's health department puts a typical boil water event at 24 to 48 hours, while adding that it can be longer and the need to boil water may last for several days or more, depending on the conditions that caused it, how quickly they can be corrected, and how long laboratory results take.

If what brought you here is how your water looks, smells or tastes rather than a notice about your water system, start somewhere else: diagnose your tap water by symptom.

If your household drinks from a private well, that is the part of this site written for it: private well water testing by county.

Boil water advisories by state

Every jurisdiction has a page of its own, naming the agency we checked and what our own records hold for it.

Check a single ZIP code for a boil water advisory

The three questions people ask next

Each of these takes one question and answers it in full.

Frequently asked questions

What does a boil water advisory mean?

It means the water system serving your address has told you to boil your tap water before using it, because boiling kills the germs the notice is about. CDC describes it as one of three kinds of drinking water advisory, and it is the only one of the three where boiling is the answer. New York State's health department lists the usual triggers as loss of pressure in the distribution system, loss of disinfection, water line breaks, treatment disruptions, power outages and floods.

How long does a boil water advisory last?

New York State's health department says a boil water event typically lasts 24 to 48 hours, but that it can be longer and the need to boil water may last for several days or more. What decides it is the condition that caused the notice, how quickly that can be corrected, and how long laboratory results take. Indiana's environmental agency describes the lifting test for an E. coli event: the advisory may only be lifted when two consecutive sets of samples, collected 24 hours apart, are found to be satisfactory.

How long do I have to boil the water for?

Bring it to a full rolling boil for 1 minute, which is the figure CDC and EPA both give. If you are above about 5,000 feet, boil for 3 minutes — EPA sets that trigger at altitudes above 5,000 feet (1,000 meters) and CDC sets it at elevations above 6,500 feet, and the more protective figure is the one to use. Then let it cool before you use it; New York State's health department notes it may take 30 minutes to cool. If your own utility's notice asks for longer, follow the notice.

Can I use my water filter instead of boiling?

No. CDC's instruction is to boil your tap water even if you filter it, New York State's health department answers the question with a flat "No!", and Louisiana's fact sheet gives the reason: most kitchen and other household water filters do not remove bacteria or viruses. Florida's guidance agrees. A filter and a boil are not alternatives to each other here.

Is a do not drink advisory the same thing?

No, and treating the two the same way is dangerous. CDC's do not drink advisory tells you to use commercially bottled water for drinking and cooking, because swallowing chemicals or toxins in the water could make you sick — and boiling does not help, since EPA states that boiling or disinfection will not destroy other contaminants such as heavy metals, salts, and most other chemicals. A do not use advisory goes further: commercially bottled water for all purposes, because swallowing, touching or having other contact with the water could be dangerous.

Sources

By TapWaterData Editorial

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