Boiling tap water kills germs but does not remove chemicals
Boiling tap water makes it safer to drink by killing bacteria, viruses, and parasites that cause illness. Heat above 160°F (71°C) starts to kill most pathogens, and a rolling boil at 212°F (100°C) kills nearly all of them within one minute. If your tap water comes from a municipal system that is already treated and tested, boiling adds an extra safety layer against biological contamination.
However, boiling does not remove chemical contaminants. Substances like lead, nitrates, pesticides, chlorine, and fluoride remain in the water after boiling—and some actually become more concentrated as water evaporates. If your water contains lead from old pipes or chemical pollution from industrial sources, boiling will not make it safe.
Key Takeaways
- Boiling kills bacteria, viruses, and parasites but leaves behind chemical contaminants like lead and nitrates.
- Municipal tap water in the United States is already tested and treated, so boiling adds protection mainly in situations where you suspect biological contamination.
- If you have lead pipes, a private well, or water that tastes or smells unusual, boiling alone is not enough—you need testing or a filter designed for that specific problem.
- Boiling for one minute at a rolling boil is effective; boiling longer does not improve safety and wastes energy.
When boiling is actually useful
Boiling works best in specific situations. If you receive a boil-water notice from your water utility, boiling is the standard emergency response. These notices go out when the system detects or suspects bacterial contamination, and boiling for one minute kills the pathogens before they reach your stomach.
Boiling also helps if you have a private well that is not regularly tested, if you are traveling to a country where water treatment is unreliable, or if you suspect recent contamination from a broken pipe or flooding. In these cases, the risk is biological, and heat solves it.
If your tap water straightforward tastes chlorinated or you want to remove chlorine taste before drinking, boiling or letting water sit uncovered for a few hours will allow chlorine to evaporate. This is a comfort choice, not a safety requirement.
What boiling does not fix
Lead is the most common reason boiling fails. Lead leaches from old pipes and solder into water, especially in homes built before 1986. Boiling concentrates lead rather than removing it. If you suspect lead, have your water tested through your local health department or a certified lab—testing costs $20 to $50 and takes a few days.
Nitrates from fertilizer or septic systems also survive boiling. High nitrate levels are especially dangerous for infants under six months old. Pesticides and industrial chemicals like PFOA (used in non-stick cookware manufacturing) do not break down in heat. Fluoride, added to many municipal systems for dental health, remains after boiling.
If your water smells like rotten eggs (hydrogen sulfide), tastes salty, or looks cloudy or discolored, boiling will not solve the underlying problem. These signs point to specific contaminants that require testing and often a filter matched to that contaminant.
How to boil water safely
Bring water to a rolling boil—vigorous bubbles breaking the surface—and keep it at that temperature for at least one minute. At high elevations above 6,500 feet, boil for three minutes because water boils at a lower temperature and takes longer to kill pathogens.
Let boiled water cool before drinking or storing it. Cover the pot while it cools to keep dust and insects out. Store cooled boiled water in a clean, covered container in the refrigerator; it stays safe for three days.
Do not re-boil water that has already cooled. Each time you heat water, minerals and any remaining contaminants concentrate further. If you need more boiled water, start with fresh tap water.
When to get your water tested
Your municipal water utility tests tap water regularly and publishes results in an annual water quality report, usually available on their website or by phone. If you want to know what is in your specific tap water at home, you can request a test through your local health department or hire a certified lab.
Test your water if you have lead pipes or solder (homes built before 1986), a private well, water that tastes or smells wrong, or a recent plumbing repair. Testing typically costs $15 to $100 depending on how many contaminants you check for. Results tell you exactly what you are dealing with and whether boiling, a filter, or professional treatment is the right solution.
Filters versus boiling
If testing shows chemical contamination, a filter is more effective than boiling. Different filters remove different things: activated carbon filters reduce chlorine taste and some pesticides; reverse osmosis removes lead, nitrates, and fluoride; and specialized filters target specific contaminants. A basic pitcher filter costs $20 to $40 and lasts two to three months; under-sink or whole-house systems cost more but treat all your water.
Boiling and filtering are not either-or choices. Some people boil for biological safety and use a filter for chemical removal. Others use a filter alone if their water is municipally treated and they trust the system. The right approach depends on what is actually in your water.
Municipal water is already treated
If you get water from a city or county system, it has already been through treatment plants that remove most bacteria, viruses, and chemicals before it reaches your home. The EPA sets standards for what is allowed in drinking water, and utilities test regularly to meet those standards. Boiling adds a safety margin, but it is not necessary for water that comes from a reliable municipal source.
That said, water quality can vary between neighborhoods, especially in older cities where pipes are aging. A boil-water notice means something went wrong—a pipe broke, pressure dropped, or contamination was detected—and boiling is the quick fix while the utility repairs the system.
Frequently Asked Questions
Does boiling remove chlorine from tap water?
Yes. Chlorine evaporates when water is heated. Boiling for a few minutes removes most chlorine taste and smell. You can also leave tap water uncovered at room temperature for several hours and chlorine will evaporate on its own, though boiling is faster.
Is it safe to boil and re-boil the same water?
It is safe but not recommended. Each time you boil water, minerals and any contaminants that do not evaporate become more concentrated. If you need more boiled water, start fresh with new tap water rather than re-boiling what is left.
Can I boil well water to make it safe?
Boiling kills bacteria and parasites in well water, but it does not remove nitrates, pesticides, or minerals. Have your well tested by a certified lab before relying on boiling alone. Well water is not regulated the way municipal water is, so testing is your only way to know what you are drinking.
How long does boiled water stay safe in the fridge?
Boiled water stays safe for three days if you store it in a clean, covered container in the refrigerator. After three days, bacteria can begin to grow again. Label the container with the date so you know when to use it.
What should I do if I got a boil-water notice?
Boil tap water for one minute before drinking, cooking, or brushing teeth. Use boiled water for ice, pet water, and baby formula. The notice will tell you when the system is safe again—usually after the utility repairs the problem and tests the water. Follow the utility's instructions for how long to boil.