Boiling is one of the simplest ways to disinfect water during a boil water advisory, but it is important to understand exactly what boiling can—and cannot—do.
Quick answer: Boiling water can inactivate many disease-causing organisms, but it does not remove lead, arsenic, nitrates, salts, pesticides, fuel, or many other chemical contaminants. In other words, boiling disinfects water; it does not fully purify it.
If your local water utility issues a boil water advisory, follow its instructions first. In general, bring clear water to a full rolling boil for 1 minute. At elevations above 6,500 feet, boil it for 3 minutes.
This guide explains how long to boil water, what boiling accomplishes, what it leaves behind, and how boiling differs from filtration and other water-treatment methods.
In This Guide
How Long Should You Boil Water?
If you are under an official boil water advisory, always follow the instructions issued by your water utility, local health department, or other responsible authority.
General CDC guidance is to:
- Use clear water whenever possible.
- Bring the water to a full rolling boil.
- Continue boiling for at least 1 minute.
- At elevations above 6,500 feet, bring to a boil and boil for 3 minutes.
- Allow the water to cool naturally.
- Store it in clean, sanitized containers with tight-fitting lids.
You do not normally need to boil water for 5, 10, or 20 minutes. During a typical boil-water advisory, follow the duration specified by public health authorities. Longer boiling also causes more water to evaporate.
What Does Boiling Water Actually Do?
Boiling is primarily a method of water disinfection.
Heat can inactivate many microorganisms that may cause waterborne illness. This is why boiling is commonly recommended when a public water system has experienced a loss of pressure, treatment disruption, or another event that raises concerns about microbial contamination.
Boiling has several practical advantages:
- It requires no specialized water-treatment equipment.
- It can be performed with a pot and reliable heat source.
- It is widely understood and relatively easy to perform correctly.
- It can be an effective temporary measure during certain water advisories.
However, disinfection and purification are not the same thing.
What Doesn't Boiling Water Remove?
Boiling does not physically remove most dissolved contaminants from water.
For example, boiling is not a reliable treatment for:
- Lead
- Arsenic
- Mercury
- Nitrates and nitrites
- Salt
- Many pesticides and herbicides
- Many industrial chemicals
- Fuel and petroleum contamination
- Many dissolved minerals and solids
When water evaporates during boiling, many dissolved substances remain in the pot. As a result, their concentration in the remaining water can sometimes increase slightly.
Important: A boil water advisory is generally issued for a microbial concern. If officials issue a do not drink or do not use advisory because of fuel, toxic chemicals, radioactive material, or another hazardous contaminant, boiling will not make the water suitable. Follow the exact advisory issued for your area.
For an overview of various drinking water concerns, see our Drinking Water Contaminants Reference Guide.
Boiling Water vs. Filtering Water
Boiling and filtration are different treatment methods designed to address different problems.
| Method | Common Uses | Important Limitations |
|---|---|---|
| Boiling | Temporary microbial disinfection, including during many boil water advisories | Does not remove many dissolved chemicals, metals, salts or minerals |
| Activated Carbon | Commonly used for chlorine-related taste and odor and selected organic compounds | Performance varies greatly by filter and does not replace boiling during an advisory |
| Reverse Osmosis | Can reduce many dissolved ions, salts and selected contaminants | Requires maintenance and usually water pressure; performance varies by system |
| Distillation | Separates water from many dissolved minerals and nonvolatile substances | Slow and energy-intensive; volatile compounds may require additional treatment |
Neither boiling nor filtering should be treated as a universal solution. The correct treatment method depends on what is actually in the water.
For a more detailed comparison, see our Guide to Drinking Water Filtration Systems.
When Should You Boil Tap Water?
The most important reason to boil tap water is an instruction from your local water utility or public-health authority.
A boil water advisory may be issued after events such as:
- A water-main break
- Loss of water pressure
- Flooding
- Storm damage
- Treatment-system problems
- Possible microbial contamination
During an advisory, boiled or appropriately bottled water may be recommended for activities such as:
- Drinking
- Preparing food
- Making ice
- Brushing teeth
- Washing fruits and vegetables
- Preparing infant formula
Exact instructions can vary, so follow the advisory issued for your area.
What About Coffee Makers and Refrigerators?
Do not assume that a refrigerator filter, coffee maker, ice maker, pitcher filter, or similar appliance makes water exempt from a boil water advisory.
Unless local officials specifically state otherwise, water from these devices should still be treated in accordance with the advisory.
Can You Use Filtered Water During a Boil Water Advisory?
A household water filter does not normally replace an official boil-water instruction.
CDC specifically advises people to boil tap water even if it has passed through a home water filter or filtering pitcher. If your utility tells customers to boil their water, follow that instruction unless the responsible authority specifically says otherwise.
During a boil-water advisory, local public health instructions take priority over normal filter use.
How to Boil Cloudy Water
If water is cloudy or contains visible particles, clarify it before boiling whenever possible.
- Allow suspended material to settle if necessary.
- Pour the clearer water through a clean cloth, paper towel, or coffee filter.
- Transfer the clarified water to a clean pot.
- Bring it to a full rolling boil.
- Boil for 1 minute, or 3 minutes above 6,500 feet.
- Allow the water to cool naturally.
- Store it in a clean, covered container.
If the water is cloudy because of a chemical spill, fuel contamination, flooding, or another potentially hazardous event, clarification and boiling may not be sufficient. Follow local instructions instead.
Does Boiling Remove Specific Drinking-Water Contaminants?
Does Boiling Remove Lead?
No. Boiling does not remove lead.
Because some of the water evaporates while lead remains behind, boiling can increase its concentration in the remaining water.
If lead is a concern, see our Lead in Drinking Water Guide.
Does Boiling Remove Arsenic?
No. Boiling is not a treatment for arsenic in drinking water.
See our Arsenic in Drinking Water Guide.
Does Boiling Remove Nitrates?
No. Boiling does not remove nitrate from water and can increase its concentration as water evaporates.
This distinction is particularly important for households using private wells.
See our Nitrates in Drinking Water Guide.
Does Boiling Remove Pesticides?
Boiling should not be relied upon to remove pesticides or herbicides from drinking water.
Different compounds behave differently during heating, and boiling is not a substitute for treatment specifically designed and tested for the chemical involved.
Does Boiling Remove PFAS?
Boiling is not an appropriate method for removing PFAS from drinking water. Because water evaporates while PFAS remain, boiling should not be expected to reduce PFAS concentration.
See our PFAS in Drinking Water Guide.
Does Boiling Remove Salt?
No. Ordinary boiling does not remove salt. The salt remains behind as water evaporates.
Distillation is different because the water vapor is captured and condensed into a separate container.
Does Boiling Remove Chlorine?
Heating and boiling can reduce some free chlorine because chlorine can dissipate from water.
However, boiling is generally inconvenient as an everyday solution when the main concern is chlorine-related taste or odor. Filtration designed for chlorine reduction is typically more practical.
See our Chlorine in Drinking Water Guide.
Does Boiling Remove Microplastics?
Boiling should not be treated as a reliable general-purpose method for removing microplastics from drinking water.
Particle behavior varies with size, water chemistry, and treatment conditions. If microplastics are your concern, look for treatment methods supported by appropriate performance data rather than assuming boiling removes them.
Why Does Boiled Water Sometimes Taste Flat?
Boiled water can taste different because heating drives dissolved gases out of the water.
Once boiled water has cooled, pouring it back and forth between two clean containers can aerate it and may improve the taste.
What If You Cannot Boil Water?
In situations where boiling is recommended but no heat source is available, public health authorities may provide instructions for chemical disinfection.
Because bleach concentration and formulation vary, do not guess the dosage. Follow current instructions from the CDC, EPA, or your local health authority.
Chemical disinfection, like boiling, is primarily intended to address biological contamination and does not remove many chemical contaminants.
Should You Filter Water After Boiling?
There is no universal requirement to filter water after it has been properly boiled during an advisory.
The correct sequence depends on the problem being addressed.
If water contains visible particles, clarification or pre-filtering may be appropriate before boiling. If you also have a separate chemical or taste concern, an appropriate filtration system may have a role—but it does not replace the boil-water instructions issued by authorities.
Where Do Berkey® Water Filters Fit?
Berkey® water filter systems are countertop gravity-fed filtration systems that operate without electricity or a permanent plumbing connection. For normal household use, performance depends on the exact filter element installed and the substance of concern.
An official boil-water advisory is different from ordinary day-to-day filtration.
If a boil water advisory is in effect, do not use normal Berkey® filtration as a substitute for the advisory. CDC advises boiling tap water even when it has already passed through a home filter. Use bottled water or water prepared according to the instructions from your utility or health department.
Once the advisory has been lifted, follow any utility instructions for flushing household plumbing and appliances. If water has been run through a household filter during the advisory, check the filter manufacturer's current guidance before returning it to normal service.
For everyday filtration rather than an active advisory, you can compare Berkey® water filter systems or review our Berkey® Filter Test Results to understand the documented performance of specific filter elements.
Frequently Asked Questions
Does boiling water make it completely pure?
No. Boiling can disinfect water by inactivating many microorganisms, but it does not remove many dissolved chemicals, metals, salts, or minerals.
How long should I boil tap water?
General CDC guidance is to bring clear water to a rolling boil for 1 minute. Above 6,500 feet, boil it for 3 minutes. If an official advisory gives different instructions, follow the advisory.
Do I need to boil water for 10 minutes?
Not under ordinary CDC boil-water guidance. Longer boiling is generally unnecessary and increases evaporation.
Should I boil filtered water during a boil water advisory?
Yes, unless local authorities specifically state otherwise. CDC advises boiling tap water even if it has already passed through a home water filter or filtering pitcher.
Does boiling water remove lead?
No. Lead remains in the water, and its concentration may increase as some water evaporates.
Does boiling water remove arsenic?
No. Boiling is not an appropriate treatment for arsenic.
Does boiling water remove nitrates?
No. Boiling does not remove nitrate and can increase its concentration in the remaining water.
Does boiling water remove chlorine?
Boiling can reduce some free chlorine, but it is generally an inconvenient method for routine chlorine taste-and-odor issues.
Does boiling remove pesticides?
Boiling should not be relied upon to remove pesticides or other chemical contaminants. Treatment should be selected for the specific substance involved.
Does boiling remove PFAS?
No. Boiling is not an appropriate PFAS treatment method and may concentrate nonvolatile substances as water evaporates.
Does boiling remove salt from water?
No. Salt remains behind during ordinary boiling. Distillation removes water as vapor and collects it separately; it is a different process.
Can I drink water immediately after boiling it?
Allow it to cool to a suitable temperature first. Store cooled water in a clean, sanitized container with a tight-fitting lid.
Why does boiled water taste different?
Boiling removes some dissolved gases, which can make the water taste flat. Aerating cooled water by pouring it between clean containers may improve the taste.
Can I use a refrigerator filter instead of boiling water?
Not during a boil water advisory unless the responsible public health authority specifically says you can.
Is boiling better than filtering?
Neither is universally better. Boiling is primarily a disinfection method, while different filters are designed to address different particles, chemicals, tastes, odors, or dissolved substances.
Final Answer: Does Boiling Water Purify It?
Boiling disinfects water, but it does not completely purify it.
During many boil water advisories, boiling is an effective, temporary measure to address microbial concerns. General guidance is to bring clear water to a rolling boil for 1 minute, or for 3 minutes at elevations above 6,500 feet.
But boiling does not remove contaminants such as lead, arsenic, nitrates, salts, PFAS, and many pesticides and industrial chemicals. Those concerns require treatment appropriate to the particular substance.
The treatment method should match the problem. Use boiling water when public health authorities instruct you to boil water. For everyday water-quality concerns, review your local water information or test results and choose filtration or treatment based on what you actually want to reduce.