Boiling kills most pathogens, but not all contaminants

Boiling water does kill bacteria, viruses, and parasites that cause waterborne illness — heat above 160°F (71°C) is lethal to most pathogens, and a rolling boil at 212°F (100°C) is more than enough. If your water source is contaminated with E. coli, salmonella, hepatitis A, or giardia, boiling for at least one minute (three minutes above 6,500 feet elevation) will render it safe to drink from a pathogen standpoint.

However, boiling does not remove chemical contaminants, heavy metals, or sediment. If your water contains lead, pesticides, nitrates, or chlorine, boiling will not eliminate them — and in some cases, boiling can concentrate certain chemicals by evaporating water and leaving contaminants behind. Boiling also does not remove salt or minerals, so it will not soften hard water or improve taste if those are your concerns.

The practical takeaway: boiling is effective for biological threats but not chemical ones. If you are dealing with a known bacterial or parasitic contamination (a boil-water notice from your utility, for example), boiling solves the problem. If you suspect chemical contamination or want to improve water quality beyond pathogen removal, you need a different method.

Key Takeaways

  • Boiling water for one minute kills bacteria, viruses, and parasites that cause waterborne illness; use three minutes if you live above 6,500 feet elevation.
  • Boiling does not remove chemical contaminants, heavy metals, sediment, or dissolved minerals, so it will not address those problems.
  • A boil-water notice from your water utility means you should boil tap water before drinking or cooking; the notice will tell you when it is safe to stop.
  • If you suspect chemical contamination, contact your water utility or use a filter designed for that specific contaminant rather than relying on boiling alone.

When a boil-water notice is issued

Your water utility issues a boil-water notice when testing detects bacteria, viruses, or parasites in the system — usually after a main break, treatment failure, or contamination event. The notice tells you to boil all water used for drinking, cooking, and brushing teeth until the utility lifts the order.

During a boil-water notice, bring water to a rolling boil and keep it boiling for one minute (three minutes if you are above 6,500 feet). Let it cool before drinking, or refrigerate it for later use. You can also use bottled water. The notice will specify an end date or tell you when to expect further instructions — do not assume it is safe to stop boiling until the utility explicitly says so.

If you receive a boil-water notice, check your utility's website or call their customer service line for details specific to your area. Some notices affect the entire system; others explore only to certain neighborhoods or water lines.

How to boil water safely

Use a pot with a lid to boil water faster and reduce energy use. Bring the water to a rolling boil — vigorous bubbles breaking the surface continuously — rather than a gentle simmer. Once it reaches a rolling boil, maintain that for one minute (or three minutes above 6,500 feet). You do not need to boil longer than that; additional time does not improve safety and wastes energy.

After boiling, let the water cool to room temperature before drinking, or transfer it to a clean container and refrigerate it. Boiled water can be stored in the refrigerator for up to three days in a covered container. Label it with the date so you know when it was boiled.

If you are boiling water regularly — because of a persistent contamination issue or because your well is untreated — consider whether a permanent solution makes sense. A point-of-use filter, a whole-house treatment system, or switching to bottled water may be more practical than boiling every day.

What boiling does not remove

Boiling concentrates some chemicals because water evaporates while contaminants remain. If your water contains nitrates (common in agricultural areas), boiling actually increases the concentration and makes it less safe. The same is true for lead, arsenic, and other heavy metals — boiling does not remove them.

Chlorine and chlorine byproducts (added by utilities to disinfect water) can be partially removed by boiling, but only if you leave the pot uncovered so gases can escape. Covering the pot traps these compounds in the water. If taste or odor from chlorine is your concern, letting tap water sit uncovered in the refrigerator overnight often works better than boiling.

Sediment, sand, and cloudiness can be reduced by letting water sit undisturbed so particles settle to the bottom, then pouring off the clear water from the top. Boiling does not remove these particles; it may actually make them more visible as water evaporates.

Alternatives to boiling

If boiling is not practical for your situation, other methods address different problems. Filters (pitcher filters, faucet-mounted filters, or under-sink systems) can remove sediment, chlorine, and some chemicals depending on the filter type. Reverse osmosis systems remove a wider range of contaminants, including heavy metals and dissolved minerals, but they are more expensive and waste some water. Distillation boils water and collects the steam, leaving contaminants behind — it removes both biological and chemical threats but is slow and energy-intensive.

If you have a private well, boiling is a temporary fix, not a long-term solution. Wells should be tested annually, and if contamination is found, you need either a treatment system or a new water source. Contact your local health department for well testing and treatment recommendations.

For municipal water, if you are concerned about quality beyond what boiling addresses, request a copy of your utility's annual water quality report (called a Consumer Confidence Report). It lists what has been detected in your water and at what levels. If you see contaminants that concern you, call your utility to discuss treatment options or use a filter designed for that specific problem.

Boiling water for cooking and food safety

Boiling water for cooking (pasta, rice, vegetables) during a boil-water notice is safe — the heat kills pathogens. However, if you are concerned about chemical contaminants in your cooking water, boiling does not help. Use bottled water for cooking if chemical contamination is a concern, or use tap water if the notice is only about biological contamination.

For baby formula, use boiled water that has cooled to room temperature, or use bottled water. If you are using well water or suspect any contamination, boil the water first and let it cool before mixing formula. Do not use boiled water that is still hot, as it can damage the formula's nutrients.

Frequently Asked Questions

How long do I need to boil water to make it safe?

Boil for one minute at a rolling boil if you are below 6,500 feet elevation. If you live above 6,500 feet, boil for three minutes because water boils at a lower temperature in higher elevations and takes longer to kill pathogens. Once the time is up, it is safe to drink.

Can I boil water in a microwave instead of on the stove?

Yes, you can microwave water until it boils, but it is harder to see when it has reached a rolling boil. Heat water in a microwave-safe container for several minutes until you see bubbles, then continue for one minute. A stovetop pot is easier to monitor and usually faster for large quantities.

Does boiled water go bad if I store it?

Boiled water stored in a clean, covered container in the refrigerator stays safe for up to three days. After that, bacteria can regrow. If you are storing boiled water, label it with the date and use it within three days. If it develops an odor or cloudiness, discard it.

What if I forget to boil my water during a boil-water notice?

If you drank unboiled water during a boil-water notice, you may have been exposed to pathogens, but infection is not certain. Watch for symptoms like diarrhea, nausea, or stomach cramps over the next few days. If symptoms appear, contact your doctor and mention the water exposure. Most waterborne illnesses resolve on their own, but some require treatment.

Is bottled water safer than boiled tap water?

Bottled water is regulated differently than tap water and may come from various sources. During a boil-water notice, bottled water is a safe alternative to boiling. For ongoing use, bottled water is safe but more expensive and generates plastic waste. Boiled tap water is equally safe for pathogens if boiled correctly.