Boil Water Advisory: What to Do When the Power and Tap Both Fail

Under a boil water advisory, the official answer is simple: use commercially bottled water, or bring your tap water to a full rolling boil for 1 minute (3 minutes above 6,500 feet) and let it cool before you use it, according to the CDC. That covers drinking, cooking, brushing your teeth, and anything else that ends up in your mouth.

The hard part comes when the same storm that broke the water main also knocked out the power. An electric stove can't boil anything in a blackout, and a camp stove only lasts as long as its fuel. That's a gap My Solar Oven can help fill, because it heats water with nothing but sunlight, and it's the heat (not the bubbles) that makes water safe.

Here is what an advisory actually means, what the official guidance says to do, what your options are when you can't boil, and where solar heat fits in.

What a boil water advisory means

A boil water notice goes out when it's possible your drinking water has been contaminated by germs that can make you sick, according to the New York State Department of Health. Their list of common causes reads like a storm checklist: loss of pressure in the water system, loss of disinfection, water line breaks, power outages, and floods.

Some notices are a precaution and some follow a bad test. North Carolina's boil water notice fact sheet, for example, covers the case where fecal coliform or E. coli bacteria turn up in the water system's samples.

The good news is that most don't last long. NYSDOH says a boil water event typically lasts 24 to 48 hours, though it can stretch to several days depending on the cause, how fast it gets fixed, and how long the lab takes to confirm the water is safe again.

It also helps to know there are three kinds of advisories, and they are not interchangeable (CDC):

• Boil water advisory: boil your tap water before you use it. Boiling kills the germs.
• Do not drink advisory: use commercially bottled water for drinking and cooking. These usually involve chemicals or toxins, and boiling will not make that water safe.
• Do not use advisory: use bottled water for everything, because even touching the tap water could be dangerous. The CDC notes these are rare.

Everything in this post is about the first kind. If your notice says "do not drink" or "do not use," heat of any kind is the wrong tool.

What the official guidance says to do

The CDC's advisory checklist is more specific than most people expect:

• Drinking and cooking: bottled or boiled water only. If you feed a baby formula, the CDC suggests ready-to-use formula if you can get it.
• Brushing teeth: boiled or bottled water, never unboiled tap water.
• Fridge water and ice: don't drink or use water or ice from dispensers connected to your water line, during any type of advisory.
• Handwashing: in many cases, tap water and soap are fine. Follow your local officials.
• Bathing: be careful not to swallow any water. For babies and young children, the CDC suggests a sponge bath.
• Dishes: disposable plates if you can. To wash by hand, wash and rinse as usual, then soak the dishes for at least one minute in 1 teaspoon of unscented household bleach per gallon of warm water, and let them air dry.
• Laundry and the garden: fine as usual.
• Pets: bottled water, or boiled water that has cooled.

Two details catch people off guard. First, your water filter doesn't get you off the hook. The CDC says to boil tap water even if it went through a home filter or a filtering pitcher, and NYSDOH says most in-home treatment devices are not designed to remove pathogens at all.

Second, dishwashers are where the agencies disagree. The CDC says dishwashers are generally safe if they have a sanitizing cycle or a final rinse of at least 150°F. The Minnesota Department of Health says home dishwashers typically don't reach temperatures that kill bacteria and shouldn't be used. When guidance conflicts, your local notice wins.

When you can't boil

This is where advisories meet real life. If the power is out and the stove is electric, here is what the official sources offer:

1. Bottled water. Every agency lists it first, and NYSDOH notes it may be the better choice when boiling isn't possible.
2. Bleach. If you can't boil, the EPA says you can disinfect with regular, unscented household bleach: 8 drops of 6% bleach or 6 drops of 8.25% bleach per gallon, stirred and left to stand 30 minutes. Double it if the water is cloudy, colored, or very cold. The water should have a slight chlorine smell afterward.
3. Disinfection tablets. Follow the label, since every product has a different strength (EPA).

There's a catch with chemicals, and it's a big one. The CDC says disinfectants don't work as well as boiling against some germs, including the parasites Cryptosporidium and Giardia. Iodine and chlorine tablets will not kill Cryptosporidium, while chlorine dioxide tablets will if you follow the instructions exactly. Portable filters have their own gap: per the CDC, they won't remove viruses.

Heat doesn't have those blind spots. According to the CDC Yellow Book, heat is a single step that inactivates all intestinal pathogens, and particles in the water don't weaken it. Its one big drawback has always been fuel.

Where heat pasteurization fits

The CDC is upfront about why the instruction is a rolling boil. Boiling isn't necessary to kill common intestinal pathogens, but it's the only easily recognizable end point that doesn't require a thermometer (CDC Yellow Book). The NYSDOH guidance for public health professionals says the same thing its own way: the term "rolling boil" assures that an effective pasteurization temperature is reached.

So the boil is a signal. The real work happens below it:

• 140°F for 30 minutes works, per the CDC Yellow Book, which notes that lower temperatures are effective with a longer contact time.
• 150°F for 20 minutes kills or inactivates the organisms that can harm people, according to studies reported by NYSDOH, including Giardia, Cryptosporidium, Salmonella, harmful E. coli strains, Hepatitis A, and rotavirus.

Here's the fun part: the CDC's own travel guidance says that in hot, sunny climates, simple reflective solar cooking can bring a container of water to pasteurization temperatures of about 150°F (CDC Yellow Book). On a clear day, My Solar Oven runs 350 to 400°F in summer and 275 to 350°F in winter, so a lidded pot of water has a lot of headroom!

We walked through the whole method, the temperatures, and the little reusable wax indicator that shows when water got hot enough in How My Solar Oven Makes Water Safe to Drink. The short version: a clean, dark, lidded pot of water goes in like any other dish, and a thermometer or a WAPI tells you when it's there. We hold to the conservative standard of 150°F for a full 20 minutes.

To be clear about where this fits: if your advisory says boil and you can boil, boil. Solar pasteurization uses the same science on a sunny day when the stove is dead and fuel is precious.

The CDC's emergency page lists one more sun-powered fallback: solar disinfection, which means filling clean, clear plastic bottles with clear water and laying them on their sides in the sun for 6 hours (or 2 days if it's cloudy). That method relies on the sun's rays rather than heat, and the CDC describes it as improving water quality by reducing germs, so treat it as a last resort.

What heat can't do

• Heat won't fix chemicals. The CDC says you cannot make water containing fuel, toxic chemicals, or radioactive materials safe by boiling or disinfecting it. Use bottled water and contact your health department.
• Boiling can concentrate some chemicals. NYSDOH warns that boiling can increase exposure to chemicals like nitrates and solvents. Along the same lines, North Carolina's health department says infants under six months and pregnant women should drink bottled water when it's available, though boiled water is still better for them than untreated water if bottled isn't an option.
• Cloudy water needs help first. Filter it through a clean cloth, paper towel, or coffee filter, or let it settle and draw off the clear water before you treat it (CDC).
• Treated water needs a clean container. Store it in clean, sanitized containers with tight covers (CDC).
• Some water is off limits. The CDC says never to use water from radiators or boilers in your home heating system for drinking, cooking, or hygiene.
• Sunlight isn't a schedule. My Solar Oven needs clear skies and direct sun. On an overcast day, bottled water and bleach are the plan, so keep both on hand.

When the advisory lifts

Don't just turn the tap back on and carry on. The Minnesota Department of Health recommends:

1. Run each cold-water faucet for five minutes, or until the water is noticeably colder.
2. Throw away any ice. If you have an icemaker, flush the feed lines and toss the first new bin.
3. Flush water heaters, water coolers, and other storage containers with at least one full tank volume.
4. Clean water softeners and filters per the manufacturer, and replace disposable filters.

North Carolina adds one more: throw out any ice or drinks made with tap water during the notice, along with any food made with it or produce washed in it.

Where My Solar Oven fits

Most boil water advisories are a day or two of inconvenience, and a few cases of bottled water handle it. The trouble starts when the advisory drags on, the power is out too, and the store shelves are bare. That's when a way to heat water without fuel stops being a nice idea and becomes a real part of the plan.

If you want a way to make water safe that doesn't depend on the grid or a fuel tank, My Solar Oven heats your water and cooks your dinner on the same sunshine. It's a lot easier to have one before the next advisory than to go looking during it.

Photo by Michal Balog on Unsplash.