Boiling tap water removes some contaminants but not all
Boiling tap water kills bacteria, viruses, and parasites that cause when ready illness. If your tap water comes from a municipal system that meets federal standards, boiling it makes it safer to drink in the short term. However, boiling does not remove chemicals, heavy metals, or mineral buildup — it can actually concentrate some of these by evaporating water and leaving dissolved solids behind.
Whether boiled tap water is safe depends on what contaminants are in your water to begin with. A water system that fails a bacterial test but passes chemical tests becomes safer when boiled. A system contaminated with lead or pesticides does not become safer — boiling leaves those substances in the water.
Key Takeaways
- Boiling kills living organisms like bacteria and viruses but does not remove chemicals, lead, or minerals dissolved in water.
- You can find out what is actually in your tap water by requesting a water quality report from your local water utility or checking their website.
- Boiling can concentrate some contaminants by reducing the volume of water, making them slightly more concentrated in what remains.
- If your water utility reports a boil-water advisory, that means boiling is the correct response for that specific problem.
What boiling actually removes from tap water
Boiling works by heating water to 212°F (100°C), which kills microorganisms. Bacteria like E. coli, viruses like norovirus, and parasites like Giardia cannot survive at that temperature. This is why public health agencies issue boil-water advisories when a water system tests positive for microbial contamination — boiling is the fastest way to make that water safe to drink while repairs are underway.
Boiling also removes some dissolved gases and volatile organic compounds (VOCs) that evaporate at high temperatures. Chlorine, which municipal systems add as a disinfectant, partially evaporates when water boils, which is why boiled tap water often tastes flatter than fresh tap water.
The process does not remove anything that does not evaporate or die from heat. Lead, nitrates, fluoride, calcium, magnesium, and most pesticides remain in the water after boiling. Some of these actually become more concentrated because the volume of water decreases as steam escapes.
When boiling makes tap water less safe
If your water contains lead — a common problem in older homes with lead pipes or solder — boiling concentrates it. As water evaporates, the lead stays behind in a smaller volume, raising its concentration. The same applies to nitrates, which can be dangerous for infants under six months old. Boiling nitrate-contaminated water makes it worse, not better.
Boiling also does not remove microplastics, which are now found in many water systems. These particles do not break down at high temperatures and pass through into the boiled water unchanged.
If you boil water in a kettle with mineral buildup, you may be adding more minerals to the water rather than removing them. Limescale and other deposits can flake into the boiled water.
How to know what is in your tap water
Your water utility is required by federal law to test tap water and publish the results in an annual water quality report, sometimes called a Consumer Confidence Report. You can request this report by phone or find it on your utility's website — search for "[your city] water quality report" or "[your county] water utility."
The report lists what contaminants were detected, at what levels, and whether those levels exceed federal safety standards. It also explains what each contaminant is and where it comes from. If the report shows bacterial contamination, boiling is the right response. If it shows lead or chemical contamination, boiling alone will not fix the problem.
If you rent and cannot reach your utility, call your local health department. They can tell you whether your water system has recent violations and what the violations were.
Boiling as a temporary measure during advisories
When a water utility issues a boil-water advisory, it means the system has tested positive for bacteria, viruses, or parasites and boiling is the recommended response. These advisories are temporary — they last until the utility repairs the problem and confirms the water is safe again through follow-up testing.
During an advisory, boil water for one minute at a rolling boil (three minutes if you live above 6,500 feet elevation, where water boils at a lower temperature). Use the boiled water for drinking, cooking, and brushing teeth. You can still shower or bathe in unboiled water — the risk from swallowing small amounts during washing is much lower than from drinking contaminated water.
Boil-water advisories usually end within a few days to a few weeks. Your utility will notify you when the water is safe again and boiling is no longer necessary.
Better options if boiling is not enough
If your water quality report shows chemical or heavy metal contamination, a water filter may be more effective than boiling. Different filters remove different things: activated carbon filters reduce chlorine and some VOCs, reverse osmosis systems remove most dissolved solids including lead and nitrates, and pitcher filters remove some but not all contaminants. Check the filter's specifications against your water report to see what it actually removes.
If you cannot afford a filter or your contamination is severe, contact your local health department or water utility about low-income information programs. Some utilities offer free or reduced-cost filters to households affected by lead contamination.
Bottled water is another option, though it is more expensive over time and creates plastic waste. Bottled water is regulated by the FDA, which has different (and sometimes less strict) standards than the EPA standards for tap water.
Common mistakes when boiling tap water
The most common mistake is boiling water in a kettle with heavy mineral deposits and assuming the boiling cleaned it. Boiling does not remove minerals — it concentrates them. If your kettle has visible white or brown buildup, descale it with vinegar or a commercial descaling product before boiling water you plan to drink.
Another mistake is boiling water and then storing it in an open container. Once boiled water cools, it can pick up new contamination from the air or container. Store boiled water in a clean, covered container in the refrigerator and use it within three days.
People also sometimes boil water longer than necessary, thinking more heat means safer water. One minute at a rolling boil is enough to kill pathogens. Boiling longer just wastes energy and concentrates dissolved solids further.
Frequently Asked Questions
Does boiling remove chlorine from tap water?
Boiling removes some chlorine because it evaporates at high temperatures, but not all of it. If you want to remove chlorine completely, let boiled water sit uncovered for 24 hours, or use an activated carbon filter. Chlorine at the levels found in municipal tap water is not harmful to drink.
Is it safe to boil tap water in a microwave?
Yes, microwaving water to boiling kills pathogens just as effectively as stovetop boiling. Heat the water for two to three minutes until it reaches a rolling boil. Be careful removing it — the container will be very hot. This method works the same way as boiling in a kettle.
Can I boil well water instead of having it tested?
Boiling well water kills bacteria and viruses but does not remove nitrates, arsenic, or other chemicals that may be present. Well water should be tested by a certified lab at least once a year, and more often if you notice changes in taste, smell, or color. Boiling alone is not a substitute for testing.
What if I boiled water and it still smells bad?
A bad smell after boiling usually means the water contains hydrogen sulfide or other gases that boiling did not fully remove, or minerals that create an odor. This is not necessarily unsafe, but it suggests your water needs testing. Contact your water utility or a certified lab to find out what is causing the smell.
Is boiled tap water safe for babies?
Boiled tap water is safe for babies if your water system is free of nitrates and lead. If your water report shows nitrate contamination, do not use boiled tap water for infant formula — use bottled water instead. Nitrates can cause a serious condition in infants under six months. Always check your water quality report before giving any tap water, boiled or not, to a baby.