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Health information notice: This page covers potential health effects associated with water contaminants. It's general information, not medical advice. Ask your doctor about risks specific to your health history.

Boil Water Advisory: What to Do and How Long It Lasts

Health disclaimer: This page provides general information about boil water advisories. It is not medical advice. Follow all instructions from your local water utility. If you have health concerns related to water exposure, contact a healthcare provider.

During a boil water advisory, use only boiled or bottled water for drinking, brushing teeth, making infant formula, and food preparation. Don't wait to change your routine.

When your utility issues a boil water advisory, that’s a formal signal that your tap water may contain bacteria or other pathogens. It doesn’t mean the water will definitely make you sick. It means something happened that compromised the system’s ability to guarantee your water is safe, and until that’s confirmed fixed, you need to treat it differently.

Here’s what you can and can’t do with the water, and what to do when the advisory lifts. For background on the bacteria that cause these advisories, see bacteria in drinking water.

What Triggers a Boil Water Advisory

Most advisories fall into a handful of categories.

A water main break is the most common cause in urban and suburban areas. When a main breaks and pressure drops, the system can’t maintain the positive pressure that keeps outside contaminants from entering the pipes. Bacteria, soil, and other material can be pulled in through cracks or joints. Even after the break is repaired, the utility needs to test before confirming the water is clear.

Low pressure events trigger the same concern even without a visible break. Unusual system demand, pump failures, or fire suppression activity can cause pressure drops that create contamination risk.

Treatment facility problems are a less common but more serious trigger. If a treatment plant has an equipment failure, chemical feed problem, or monitoring gap, the utility may not be able to confirm that water leaving the plant meets disinfection standards.

Natural disasters, flooding in particular, can overwhelm treatment systems or compromise distribution infrastructure. Advisories issued after flooding tend to last longer because the investigation is more complex and testing takes time.

And occasionally, routine monitoring simply finds unexpected bacteria in the system. That triggers a precautionary advisory while the utility investigates the source.

What You Can and Can’t Do with the Water

Knowing what’s still fine to do matters as much as knowing what to avoid.

Don’t use tap water for: drinking, brushing teeth, making ice, preparing infant formula (infant formula water safety), cooking with water that contacts food, rinsing produce, or filling a pet’s water bowl.

You can use tap water for: flushing toilets, washing dishes in a dishwasher on a high-heat cycle with a heated dry (the temperatures exceed what’s needed to kill bacteria), doing laundry, and washing hands, provided you dry them thoroughly and don’t work with food immediately after.

Showering is generally fine for healthy adults. Keep water out of your mouth, eyes, and nose. Supervise young children closely since they tend to swallow water during baths or showers. If you have an open wound, a compromised immune system, or you’re immunocompromised for any reason, talk to your doctor before showering in advisory water.

Ice from your refrigerator dispenser needs to go. That ice was made from tap water. Discard it and don’t make new ice until the advisory lifts and you’ve flushed your lines. Ice from a commercial store is made from independently treated water and is generally fine.

Pets: Use boiled or bottled water for pets’ drinking water during an advisory. Dogs and cats can get sick from the same pathogens that affect humans.

How to Boil Water Correctly

Boiling kills bacteria, viruses, and protozoa. It’s reliable when done right.

Bring water to a full rolling boil. A rolling boil means the water is bubbling vigorously throughout, not just around the edges. Hold it there for one minute. At elevations above 6,500 feet, hold it for three minutes, since water boils at a lower temperature at altitude and needs the extra time for the same effect.

Let the water cool before using it. Pouring boiling water into infant formula, for example, can destroy heat-sensitive nutrients. Cool it in a clean covered container.

Boiled water stored in a clean, sealed container stays safe for up to 24 hours at room temperature, or longer in the refrigerator. Use a container with a lid, not an open pitcher sitting on the counter.

One thing boiling doesn’t do: it doesn’t remove chemical contaminants. If the advisory is specifically about a chemical spill or industrial contamination event, boiling won’t help and may concentrate certain chemicals. In that case, bottled water is the right call. Your utility will specify if the advisory is chemical rather than microbial. See does boiling water remove contaminants? for the full breakdown.

What to Do When the Advisory Lifts

Don’t just go back to normal immediately. Your home’s plumbing trapped the potentially contaminated water, and your ice maker and refrigerator water dispenser stored it. You need to flush the system.

Run every cold water tap in your home for one to two minutes. Start with the tap farthest from your water meter and work toward it, or just run them all at once. The goal is to push the old water out and bring in fresh, treated water from the main.

Run your water heater through a cycle. The water heater holds a tank of the old water. Running hot water at taps until it gets hot flushes the tank.

Clean faucet aerators and showerhead screens. These mesh screens trap particles and can harbor bacteria. Unscrew them, rinse, and soak in a bleach solution (one tablespoon of bleach per quart of water) for five minutes before reinstalling.

Discard the ice in your refrigerator’s ice bin and any water in your refrigerator dispenser’s internal lines. Run the ice maker through a few cycles and discard those batches. Most manufacturers recommend running and discarding two or three batches after an advisory before keeping ice.

Run your dishwasher empty on a hot cycle before using it for dishes again.

If you have a refrigerator water filter, it doesn’t need replacing after a routine boil water advisory. The filter didn’t cause the problem. But run a quart of water through the dispenser to flush the lines before drinking.

Sources:

Health disclaimer: WaterAnswer.com provides general information only. Always follow your local water utility’s specific instructions during an advisory. If you have questions about exposure or health concerns, contact a healthcare provider.

Frequently Asked Questions

How long does a boil water advisory last?
It depends on the reason for the advisory. A main break advisory typically lifts within 24-72 hours once the utility confirms pressure is restored and bacteria testing passes. An advisory issued after flooding or contamination may last days to weeks while the cause is investigated and treated. Your utility will issue a formal "advisory lifted" notice. Don't assume it's over until you get that notice.
Can I shower during a boil water advisory?
Generally yes. Healthy adults can shower or bathe during a boil water advisory. Don't let water get in your eyes, nose, or mouth. Young children should be supervised carefully to prevent swallowing water. People with open wounds or compromised immune systems should check with their doctor before showering.
Can I use ice from my refrigerator during a boil water advisory?
No. Ice made from tap water before the advisory was issued may be contaminated. Discard any ice made during or before the advisory period. Ice from a commercial store that uses independently treated water is generally safe.
Can I use a Brita filter instead of boiling?
No. Standard pitcher filters, including Brita, are not designed to remove bacteria from contaminated water. Some advanced filters with ceramic filtration or specific certifications may address bacteria, but standard carbon pitcher filters don't. During a boil water advisory, boiling or commercially bottled water are the reliable options.
How do I know when the boil water advisory is lifted?
Your water utility is required to issue a formal notice when the advisory ends. Check your utility's website, call their hotline, or sign up for text/email alerts. Many utilities also notify local news outlets. Don't assume the advisory is lifted because a neighbor says so. Wait for the official notice.
Medical disclaimer: WaterAnswer.com provides general information only. Nothing on this site is medical advice. Talk to a licensed healthcare provider before making decisions about your health.