Boiling removes some contaminants but not all
Boiling tap water kills bacteria, viruses, and some parasites by exposing them to sustained heat — typically 212°F (100°C) at sea level. If your tap water contains disease-causing microorganisms, boiling for at least one minute (three minutes above 6,500 feet elevation) will make it safe from those threats.
Boiling does not remove chemical contaminants. Lead, nitrates, pesticides, chlorine byproducts, and industrial chemicals remain in the water after boiling. In some cases, boiling can actually concentrate these substances by reducing the total volume of water while the chemicals stay behind.
Whether boiling is enough depends on what is actually in your water. If your tap water fails a test for bacteria or parasites, boiling solves the problem. If it contains lead or chemical pollution, boiling alone will not.
Key Takeaways
- Boiling kills bacteria, viruses, and parasites but leaves behind lead, nitrates, pesticides, and other chemical contaminants.
- A water test from your local health department or a certified lab tells you which contaminants are present and whether boiling is sufficient.
- If boiling is your only option and you cannot test the water, boil for one minute (three minutes above 6,500 feet) and store in clean containers.
- Boiling does not remove chlorine taste or odor; a carbon filter handles that better than heat alone.
- For chemical contamination, a pitcher filter, faucet filter, or reverse osmosis system works better than boiling.
When boiling actually solves the problem
Boiling is the right answer if your water contains bacteria, viruses, or parasites. Public water systems test for these regularly, so if your local water report shows no microbial contamination, boiling is unnecessary. If you get water from a well, a private source, or you have been told there is a boil-water advisory in your area, boiling is the correct response.
A boil-water advisory is issued by your local health department when microbial contamination is detected or suspected. The advisory specifies how long to boil — usually one minute at sea level, three minutes at higher elevations. Follow the exact time and temperature given in the advisory for your location.
After boiling, let the water cool in a clean, covered container. Store it in the refrigerator and use it within three days. Boiled water can pick up new bacteria if it sits uncovered or in a dirty container.
What boiling leaves behind
Chemical contaminants pass through boiling unchanged. Lead, which leaches from old pipes and solder, remains in boiled water at the same concentration as before. Nitrates from fertilizer runoff, pesticides, and industrial chemicals like PFOA (used in non-stick coatings) are not affected by heat.
Chlorine, added by water systems to kill bacteria, does evaporate when water is boiled — so boiling actually does improve taste and odor if chlorine is the main complaint. However, chlorine byproducts like trihalomethanes (THMs) may increase slightly as chlorine breaks down under heat.
If your water report lists any chemical contaminants above safe levels, boiling will not fix it. You need either a pitcher filter with activated carbon, a faucet-mounted filter, or a reverse osmosis system under the sink, depending on which chemicals are present.
How to get your water tested
Your local water utility publishes a water quality report (called a Consumer Confidence Report) every year. Request it by phone or find it online — search "[your city] water quality report" or "[your county] public water system." The report lists all contaminants detected and their levels.
If you have a private well or suspect contamination not listed in the public report, contact your state health department or local extension office for a list of certified labs. A basic test costs $15 to $50 and checks for bacteria, nitrates, and pH. A comprehensive test that includes lead and chemicals costs $100 to $300.
Bring the test results to a water filter retailer or your health department. They can tell you whether boiling is enough or whether you need a filter.
Boiling as a temporary measure
If you cannot test your water and cannot install a filter, boiling is better than drinking untreated water. Boil for the full recommended time, cool it in a clean covered container, and refrigerate it. This protects you from microbial contamination, which is the most common acute health threat from tap water.
Boiling does not protect you from chemical contamination, but chemical contamination usually causes harm over months or years, not when ready. If you are in a situation where boiling is your only option, use it while you work toward a permanent solution — a filter, a water delivery service, or a move to a different water source.
For short-term use (a few days to a few weeks), boiling is a reasonable emergency measure. For longer periods, explore filter options or contact your local health department about other resources.
Boiling versus filtering
Boiling and filtering solve different problems. Boiling kills living organisms; filtering removes particles and chemicals. A pitcher filter with activated carbon (like Brita or PUR) removes chlorine taste, some chemicals, and sediment, but does not kill bacteria. A reverse osmosis system removes most chemicals and some bacteria, but does not kill viruses as reliably as boiling does.
If your water has both microbial and chemical contamination, you may need both methods. Boil the water first to kill organisms, then filter it to remove chemicals. Or use a filter designed for your specific contaminant and boil if bacteria is also a concern.
For most people on a public water system, boiling is unnecessary — the utility already treats the water. A pitcher filter handles taste and odor. For well water or a boil-water advisory, boiling is the first step.
Storage and safety after boiling
Boiled water cools quickly and can pick up new contamination from the air or from containers. Use clean, food-grade containers with tight lids. Glass or food-grade plastic works; do not use containers that held chemicals or pesticides.
Store boiled water in the refrigerator and use it within three days. Do not leave it on the counter at room temperature for more than a few hours. If you need to transport boiled water, keep it in a sealed container and do not let it sit in a warm car or direct sunlight.
If you are boiling water for a baby, let it cool to room temperature before use. Boiling does not remove minerals, so boiled tap water is safe for infant formula if the water itself is not contaminated with chemicals.
Frequently Asked Questions
Does boiling remove fluoride from tap water?
No. Fluoride has a much higher boiling point than water and remains in the water after boiling. If you want to remove fluoride, you need a reverse osmosis system or a specialized fluoride filter. Most public water systems add fluoride to prevent tooth decay, and boiling does not change that.
How long do I need to boil water to make it safe?
At sea level, boil for at least one minute. Above 6,500 feet elevation, boil for three minutes. Use a rolling boil, not just hot water. If a boil-water advisory is in effect in your area, follow the specific time listed in the advisory.
Can I boil water in a microwave instead of on the stove?
Yes, but it is less reliable. Microwave heating can create hot spots and cold spots, so some organisms may survive. Stovetop boiling with a rolling boil is more consistent. If you use a microwave, boil for longer — at least three to five minutes — and stir the water to distribute heat evenly.
Does boiling remove the smell of chlorine from tap water?
Yes. Chlorine evaporates when water is heated, so boiling removes chlorine odor and taste. However, if you just want to remove chlorine taste, letting tap water sit uncovered in the refrigerator overnight works just as well and uses no energy.
What if I boil water but it still tastes bad?
Bad taste after boiling usually means the water contains chemicals, minerals, or sediment that boiling does not remove. A pitcher filter with activated carbon or a faucet filter will improve taste better than boiling alone. If the taste is very bad or the water looks cloudy, have it tested before drinking it.