What should I do during a boil-water notice?

A boil-water notice (sometimes called a boil-water advisory) is a warning from your water utility or a health agency that the water coming out of your taps might contain bacteria, viruses, or parasites. Drinking or cooking with that water before treating it could make you sick. The notice is precautionary. It often goes out before any test confirms a problem, because waiting for results could leave people exposed.

Three common events trigger one. A water main break can pull dirt and germs into pipes that are normally sealed and pressurized. A loss of system pressure, from a power outage at a pump station or heavy demand during firefighting, removes the barrier that keeps outside contamination from seeping in. And a detected or suspected contamination event, such as a positive bacteria sample, can prompt a notice while the cause is traced. Federal rules back this up. The EPA's public notification requirements direct water systems to alert customers quickly when a problem could affect health, and a boil-water notice is one of those alerts.

In the Phoenix area, the City of Phoenix Water Services or your local provider issues these notices and lifts them. They will tell you the affected streets or zip codes, when the notice started, and what to do. Follow your own utility's message first, since they know exactly what triggered the alert and which neighborhoods are involved.

Heat is what makes the water safe, and the method is precise. Fill a clean pot, put it on the stove, and bring the water to a rolling boil, the kind that keeps bubbling hard even when you stir it. According to the CDC, "If you don't have safe bottled water, you should boil your water to make it safe to drink. Boiling is the surest method to kill disease-causing germs, including viruses, bacteria, and parasites." Hold that rolling boil for 1 full minute, then turn off the heat and let the water cool on its own.

Altitude changes the timing. At elevations above 6,500 feet, the CDC says to boil for 3 minutes, because water boils at a lower temperature up high and needs longer to do the same job. Phoenix sits at roughly 1,100 feet above sea level, well below that line, so the 1-minute rule applies across the metro area. If the water looks cloudy, let it settle first or filter it through a clean cloth, then boil.

A quick checklist for boiling:

• Use a clean pot and clean utensils.
• Bring water to a hard, rolling boil.
• Keep it boiling for 1 minute (3 minutes above 6,500 feet, which is not Phoenix).
• Let it cool naturally. Do not add ice to speed it up.
• Store cooled water in clean, covered containers.

Boiled water can taste flat because the air boils out of it. Pouring it back and forth between two clean containers, or adding a small pinch of salt, brings the taste back.

Boiling kills living germs, but it does not remove chemical contamination. Heat has no effect on lead, solvents, fuel, pesticides, or other chemicals, and boiling can actually concentrate some of them as water evaporates from the pot. This is the one situation where boiling is the wrong move.

So read the notice. If your utility says the water is or might be contaminated with a chemical rather than a germ, do not boil it. Use bottled water instead for drinking, cooking, and anything else listed below, and wait for specific guidance from the utility or your local health department. The EPA's emergency disinfection guidance is clear that boiling and home disinfection are for microbial threats, not chemical ones. Most boil-water notices in a city system come from pressure loss or a main break, which are germ risks, but the notice itself will state the reason. When in doubt, bottled water is the safe default.

Until the notice is lifted, treat your tap as suspect for anything that enters your body or touches food. Use boiled (then cooled) or bottled water for all of these:

• Drinking and preparing drinks.
• Cooking and washing produce.
• Brushing teeth.
• Making ice, and tossing any ice the machine already made.
• Mixing infant formula (ready-to-feed formula is a good backup).
• Filling water bowls for pets, since the same germs can sicken animals.

Some everyday uses stay safe with regular tap water. Handwashing with soap and tap water is fine for most people. Scrub for about 20 seconds and dry your hands. Bathing and showering are generally safe for adults and older children, as long as you do not swallow the water. Take extra care with babies and young kids during a bath so they do not drink it, and consider a sponge bath for infants. People with weakened immune systems, open wounds, or recent surgery should ask their doctor or follow the utility's specific advice, since their risk is higher.

For dishes, run your dishwasher only if it has a sanitizing or hot-water cycle that reaches a high temperature. Otherwise, wash by hand and add a sanitizing rinse, or use boiled water. Do laundry as normal, since clothes do not absorb water the way food and dishes do. If you want a deeper read on why your tap water is usually fine in the metro area, see our page on whether Phoenix tap water is safe to drink.

When the utility announces the water is safe again, take a few minutes to clear the old, possibly contaminated water out of your home's pipes and appliances. This step matters because water that sat in your plumbing during the notice can still carry germs.

Work through this list once the all-clear comes:

• Flush your cold-water taps. Run each cold tap for about 5 minutes to push old water out of your pipes.
• Run your hot water afterward to cycle the water heater, then flush the lines again.
• Dump all old ice and run the ice maker through one or two full cycles, discarding that ice too.
• Drain and refill water dispensers, coffee makers, and any reservoir that held tap water.
• Replace water filters in your fridge, pitcher, or under-sink system, since the old cartridge may hold trapped germs.
• Run water-using appliances like the dishwasher and washing machine through an empty cycle.
• Flush exterior faucets and irrigation lines that get used for drinking or food prep.

If your water still looks dirty, smells off, or has low pressure after flushing, hold off and call your utility. A persistent problem inside your own home, like a slow leak or a fixture that will not clear, is worth a look from a licensed plumber. HQ Plumbing & Air serves metro Phoenix 24/7 and can check your lines, fixtures, and water heater after an advisory. While you wait, our guide on what to do while waiting for a plumber walks through the safe first steps.