How to boil drinking water for safe use: here we provide the details of just how long to boil water to sterilize it for drinking purposes. We give water temperatures needed and time durations needed for safe drinking water.

Guide to Boiling Water for Drinking

This article series outlines methods to purify or sanitize drinking water in an emergency following a disaster such as an earthquake, flood, or hurricane.

If drinking water is of questionable purity, boil the water for at least five minutes, and/or add bleach, and/or distill drinking water before using if a distiller and electrical power or an alternative heat source are available. See information on water treatment under the "Disaster Supplies Kit" section of some public documents.

Boiling water can kill nearly all microorganisms except, as author Matthew Stein points out in When Technology Fails, prions - which are not often present in a water supply. Remember however that boiling water will not reliably remove most chemicals nor will it remove radioactive contamination.

Even if there has been a loss of electrical power, natural or LP gas may be available at some buildings, allowing you to boil water to produce safe drinking water in an emergency. Our page top photo shows a pot of cold water that has just been placed on a natural-gas fired stovetop to begin the boiling procedure. Tip: your water will boil faster and you'll waste less fuel if you keep a top on the container during heating.

Safety Warning: do not enter a building nor attempt to use gas appliances in a building if there is a smell of gas odors or if the gas piping and appliances have been damaged by a storm, earthquake, or other event.

In most environments, the length of time that water is exposed to temperatures of 185 degF. or higher between the time it reaches 185 degF. and the time that it reaches boiling at 212 degF. is sufficient to kill most organisms and pathogens in the water.

That's why experts have not suggested that you need to boil the water for more than a minute or so. If you are boiling water on an unusually hot powerful heat source, boil it a bit longer to be safe.

Typically, experts recommend three minutes of rolling boiling water at sea level altitude to safely disinfect water for drinking.

References on boiling drinking water for safe consumption

• Also seeReferences or Citations and additional citations at the end of this page
• Clasen, Thomas F., Do Hoang Thao, Sophie Boisson, and Oleg Shipin. "Microbiological effectiveness and cost of boiling to disinfect drinking water in rural Vietnam." Environmental science & technology 42, no. 12 (2008): 4255-4260.
  Abstract:
  
  Despite certain shortcomings, boiling is still the most common means of treating water in the home and the benchmark against which alternative household-based disinfection and filtration methods must be measured. We assessed the microbiological effectiveness and cost of boiling among a vulnerable population relying on unimproved water sources and commonly practicing boiling as a means of disinfecting water.
  
  In a 12 week study among 50 households from a rural community in Vietnam, boiling was associated with a 97% reduction in geometric mean thermotolerant coliforms (TTCs) (p < 0.001).
  
  Despite high levels of faecal contamination in source water, 37% of stored water samples from self-reported boilers met the WHO standard for safe drinking water (0 TTC/100 mL), and 38.3% fell within the low risk category (1–10 TTC/100 mL).
  
  Nevertheless, 60.5% of stored drinking water samples were positive for TTC, with 22.2% falling into the medium risk category (11–100 TTC/100 mL).
  
  The estimated cost of wood used to boil water was US$ 0.272 per month for wood collectors and US$ 1.68 per month for wood purchasers, representing approximately 0.48% to 1.04%, respectively, of the average monthly income of participating households.
• Cohen, Alasdair, Qi Zhang, Qing Luo, Yong Tao, John M. Colford Jr, and Isha Ray. "Predictors of drinking water boiling and bottled water consumption in rural China: a hierarchical modeling approach." Environmental science & technology 51, no. 12 (2017): 6945-6956.
  Abstract:
  Approximately two billion people drink unsafe water. Boiling is the most commonly used household water treatment (HWT) method globally and in China. HWT can make water safer, but sustained adoption is rare and bottled water consumption is growing. To successfully promote HWT, an understanding of associated socioeconomic factors is critical. We collected survey data and water samples from 450 rural households in Guangxi Province, China.
  
  Covariates were grouped into blocks to hierarchically construct modified Poisson models and estimate risk ratios (RR) associated with boiling methods, bottled water, and untreated water. Female-headed households were most likely to boil (RR = 1.36, p < 0.01), and among boilers those using electric kettles rather than pots had higher income proxies (e.g., per capita TV ownership RR = 1.42, p < 0.01). Higher-income households with younger, literate, and male heads were more likely to purchase (frequently contaminated) bottled water, or use electric kettles if they boiled.
  
  Our findings show that boiling is not an undifferentiated practice, but one with different methods of varying effectiveness, environmental impact, and adoption across socioeconomic strata. Our results can inform programs to promote safer and more efficient boiling using electric kettles, and suggest that if rural China’s economy continues to grow then bottled water use will increase.
• Crampton, Andrea, and Angela T. Ragusa. "Exploring perceptions and behaviors about drinking water in Australia and New Zealand: is it risky to drink water, when and why?." Hydrology 3, no. 1 (2016): 8.
• Galway, Lindsay P. BOILING OVER: A DESCRIPTIVE ANALYSIS OF DRINKING WATER ADVISORIES IN FIRST NATIONS COMMUNITIES IN ONTARIO, CANADA [PDF] International journal of environmental research and public health 13, no. 5 (2016): 505.
  Abstract
  Access to safe and reliable drinking water is commonplace for most Canadians. However, the right to safe and reliable drinking water is denied to many First Nations peoples across the country, highlighting a priority public health and environmental justice issue in Canada. This paper describes trends and characteristics of drinking water advisories, used as a proxy for reliable access to safe drinking water, among First Nations communities in the province of Ontario. Visual and statistical tools were used to summarize the advisory data in general, temporal trends, and characteristics of the drinking water systems in which advisories were issued.
  
  Overall, 402 advisories were issued during the study period. The number of advisories increased from 25 in 2004 to 75 in 2013. The average advisory duration was 294 days. Most advisories were reported in summer months and equipment malfunction was the most commonly reported reason for issuing an advisory. Nearly half of all advisories occurred in drinking water systems where additional operator training was needed. These findings underscore that the prevalence of drinking water advisories in First Nations communities is a problem that must be addressed. Concerted and multi-faceted efforts are called for to improve the provision of safe and reliable drinking water First Nations communities.
• Heitzinger, Kristen, Claudio A. Rocha, Robert E. Quick, Silvia M. Montano, Drake H. Tilley Jr, Charles N. Mock, A. Jannet Carrasco, Ricardo M. Cabrera, and Stephen E. Hawes. "“Improved” but not necessarily safe: an assessment of fecal contamination of household drinking water in rural Peru." The American journal of tropical medicine and hygiene 93, no. 3 (2015): 501-508.
• Juran, Luke, and Morgan C. MacDonald. "An assessment of boiling as a method of household water treatment in South India." Journal of water and health 12, no. 4 (2014): 791-802.
  Abstract:
  This article scrutinizes the boiling of water in Tamil Nadu and Puducherry, India. Boiling, as it is commonly practiced, improves water quality, but its full potential is not being realized. Thus, the objective is to refine the method in practice, promote acceptability, and foster the scalability of boiling and household water treatment (HWT) writ large.
  
  The study is based on bacteriological samples from 300 households and 80 public standposts, 14 focus group discussions (FGDs), and 74 household interviews. Collectively, the data fashion both an empirical and ethnographic understanding of boiling. The rate and efficacy of boiling, barriers to and caveats of its adoption, and recommendations for augmenting its practice are detailed.
  
  While boiling is scientifically proven to eliminate bacteria, data demonstrate that pragmatics inhibit their total destruction. Furthermore, data and the literature indicate that a range of cultural, economic, and ancillary health factors challenge the uptake of boiling.
  
  Fieldwork and resultant knowledge arrive at strategies for overcoming these impediments. The article concludes with recommendations for selecting, introducing, and scaling up HWT mechanisms. A place-based approach that can be sustained over the long-term is espoused, and prolonged exposure by the interveners coupled with meaningful participation of the target population is essential.
• Mintz, Eric D., Fred M. Reiff, and Robert V. Tauxe. "Safe water treatment and storage in the home: a practical new strategy to prevent waterborne disease." Jama 273, no. 12 (1995): 948-953.
  
  Watch out: Excerpt: After cooling, boiled water can easily be re- contaminated, especially if it is transferred to a storage container.
• New York DOH, Boil Water Notices - Fact Sheet and Templates for Public Drinking Water Suppliers [PDF] New York State Department of Health, original source: https://www.health.ny.gov/environmental/water/drinking/boilwater/boil_water_fact_sheet.htm
  Excerpt:
  Q16 - How long should water be boiled to make it potable? Drinking water should be brought to a FULL ROLLING BOIL for ONE MINUTE and then COOLED BEFORE USE. Boiling is a form of pasteurization. The term rolling boil facilitates communication and helps assure that an effective pasteurization temperature is reached. Research has established that boiling for one minute is very effective in destroying pathogens, including viruses, bacteria and protozoa such as Cryptosporidium and Giardia. The USEPA and the Centers for Disease Control have both endorsed a one minute boiling time for drinking water.
• New York DOH, Boil Water Response - Information for the Public Health Professional [PDF] (2021) New York State Department of Health, retrieved 2021/04/13 original source: https://www.health.ny.gov/environmental/water/drinking/boilwater/response_information_public_health_professional.htm
  Excerpt:
  
  Although, some bacterial spores not typically associated with water borne disease are capable of surviving boiling conditions (e.g. clostridium and bacillus spores), research shows that water borne pathogens are inactivated or killed at temperatures below boiling (212°F or 100°C).
  
  In water, pasteurization is reported to begin at temperatures as low as 131°F/55°C for protozoan cysts.
  
  Similarly, it is reported that one minute of heating to 162°/72°C and two minutes of heating at 144°/62°C will render Cryptosporidium oocysts non-infectious.
  
  Other studies report that water pasteurized at 150°F/65°C for 20 minutes will kill or inactivate those organisms that can cause harm to humans. These include: Giardia, Cryptosporidium, Endameba, the eggs of worms, Vibrio cholera, Shigella, Salmonella bacteria, those that cause typhoid, the enterotoxogenic strains of E. coli, Hepatitis A and rotaviruses.
  
  It is also reported that a 99.999% kill of water borne microorganisms can be achieved at 149°F/65°C in five minutes of exposure.
  
  Water will boil at different temperatures under different conditions (e.g. lower temperatures at higher elevations, higher temperatures in pressure vessels), however these differences are not a significant factor for boil water responses. Water in an open vessel will boil at about 212°F/100°C in New York.
  
  Even on the top of Mt. Marcy, NY where the elevation is more than one mile above sea level, water boils at about 203°F/95°C and is adequate for disinfecting water.
• O'Donnell, M., C. Platt, and R. Aston. EFFECT OF A BOIL WATER NOTICE ON BEHAVIOUR IN THE MANAGEMENT OF A WATER CONTAMINATION INCIDENT [PDF] Communicable Disease and Public Health 3, no. 1 (2000): 4.
  
  Summary:
  
  In late 1998, the water supply of 878 households was affected by possible sewage contamination. A notice was issued to advise residents of the need to boil their water. This provided an opportunity to assess to what extent the boil water notice led people to avoid activities that might put them at risk of waterborne infection. A postal questionnaire sent to 350 randomly selected households in the affected area asked about timing and mode of receipt of the notice, risk behaviour (boiling water, brushing teeth, washing dishes, drinks for pets, preparation of food), and subsequent changes in drinking water consumption habits.
  
  Eighty-one per cent of the households surveyed engaged in behaviour likely to increase the risk of waterborne infection. Comments were collected from consumers on how to improve the management of future water contamination incidents.
• Oswald, William E., Andrés G. Lescano, Caryn Bern, Maritza M. Calderon, Lilia Cabrera, and Robert H. Gilman. "Fecal contamination of drinking water within peri-urban households, Lima, Peru." The American journal of tropical medicine and hygiene 77, no. 4 (2007): 699-704.
• Rosa, Ghislaine, Laura Miller, and Thomas Clasen. MICROBIOLOGICAL EFFECTIVENESS OF DISINFECTING WATER BY BOILING IN RURAL GUATEMALA [PDF] The American journal of tropical medicine and hygiene 82, no. 3 (2010): 473-477.
  Discussion excerpt:
  Our results show that the practice of boiling in the study community significantly improves the microbiological quality of water, but does not fully remove the potential risk of waterborne pathogens.
  
  Although the 86.2% reduction observed here is lower than the 99% and 97% reductions reported in similar studies in India and Vietnam,6,13 this was largely a function of a lower level of contamination in the source water; the mean level of contamination in stored water that was reportedly boiled was similar in Guatemala (2.2 TTC/100 mL) to that in India (4.2) and Vietnam (5.8).
  
  As in the previous studies, we also observed a substantial shift in the risk profile of treated versus stored water. Over 70% of boiled water samples were free of TTC, only 4.9% of samples contained high (101–1,000) levels and none contained very high (> 1,000) levels.
• Psutka, Rebecca, Rachel Peletz, Sandford Michelo, Paul Kelly, and Thomas Clasen. "Assessing the microbiological performance and potential cost of boiling drinking water in urban Zambia." Environmental science & technology 45, no. 14 (2011): 6095-6101.
  Abstract
  
  Boiling is the most common method of disinfecting water in the home and the benchmark against which other point-of-use water treatment is measured. In a six-week study in peri-urban Zambia, we assessed the microbiological effectiveness and potential cost of boiling among 49 households without a water connection who reported “always” or “almost always” boiling their water before drinking it.
  
  Source and household drinking water samples were compared weekly for thermotolerant coliforms (TTC), an indicator of fecal contamination. Demographics, costs, and other information were collected through surveys and structured observations.
  
  Drinking water samples taken at the household (geometric mean 7.2 TTC/100 mL, 95% CI, 5.4–9.7) were actually worse in microbiological quality than source water (geometric mean 4.0 TTC/100 mL, 95% CI, 3.1–5.1) (p < 0.001), although both are relatively low levels of contamination.
  
  Only 60% of drinking water samples were reported to have actually been boiled at the time of collection from the home, suggesting over-reporting and inconsistent compliance. However, these samples were of no higher microbiological quality.
  
  Evidence suggests that water quality deteriorated after boiling due to lack of residual protection and unsafe storage and handling. The potential cost of fuel or electricity for boiling was estimated at 5% and 7% of income, respectively. In this setting where microbiological water quality was relatively good at the source, safe-storage practices that minimize recontamination may be more effective in managing the risk of disease from drinking water at a fraction of the cost of boiling.
• Sari, Sri Yusnita Irda, Azyyati Ridha Alfian, Titik Respati, Dwi Agustian, and Ardini Saptaningsih Raksanagara. "Comparison of Drinking Water Quality Following Boiling, Household Filtration and Water-Refill in Urban-Slum Area." Journal of International Dental and Medical Research 12, no. 2 (2019): 791-796.
  
  Abstract
  Safe drinking water availability remains crucial problem in urban-slum areas. Boiling and household filtration are the most frequent water-treatment methods; water-refill is a growing industry providing affordable drinking water for low-middle income households in developing countries. This study compared the efficacy and annual infection risk after boiling, filtration, and water-refill methods to determine the best method for urban-slum dwellers. It was quasiexperimental pre-post design, data were collected by purposive sampling from urban-slum area in Bandung municipality between January-February 2017. Water samples were examined from 55 households using boiling and filtration method and 55 households using water-refill. Coliforms and E.coli contaminations were examined using membrane filter method. The removal efficacy of Coliforms, log removal reduction (LRR) and annual risk infection were calculated. The efficacy of filtration for removing Coliform/E.coli was 99.84% and 100%, boiling was 98% and 96%, respectively. Only 54.5% of water-refill samples were Coliformnegative. Safe LRR for Coliforms/E. coli using filtration was 76.63% and 100% whereas using boiling was 40% and 96.36%, respectively. Only household filtration demonstrated no annual risk infection. Household filtration is the most effective method to eliminate microorganisms from raw water. Health education and proper water-treatment method promotion are warranted to prevent waterborne disease in urban-slum areas
• U.S. CDC MAKING WATER SAFE IN AN EMERGENCY [PDF] U.S. CDC, retrieved 2021/04/13 original source: https://www.cdc.gov/healthywater/emergency/making-water-safe.html
  Excerpt:
  If the water is clear, [or has been filtered to make it clear] bring the clear water to a rolling boil for 1 minute (at elevations above 6,500 feet, boil for three minutes).
• U.S. EPA, EMERGENCY DISINFECTION of DRINKING WATER [PDF] U.S. EPA, retrieved 2021/04/13 original source: https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water
  Excerpt:
  If water is cloudy, let it settle and filter it through a clean cloth, paperboiling water towel, or coffee filter.
  Bring water to a rolling boil for at least one minute. At altitudes above 5,000 feet (1,000 meters), boil water for three minutes.
• Verhille, Sophie. UNDERSTANDING MICROBIAL INDICATORS FOR DRINKING WATER ASSESSMENT: INTERPRETATION OF TEST RESULTS AND PUBLIC HEALTH SIGNIFICANCE [PDF] National Collaborating Centre for Environmental Health (2013): 1-12.
  
  Excerpt: The non-detection of E.coli does not guarantee that water is safe to drink because a water sample is only a snapshot1,21 of the water being distributed and because some organisms are more resistant to chlorine/disinfectant than the indicator E.coli.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-04-13 by (mod) - reader disagrees with boiling drinking water for more than one minute

@Anon,

Thank you for catching and challenging the text of this page - indeed it needs clarification and perhaps outright need correction just as you suggest. I'll review and edit the text for clarity and make sure it's correct.

I agree that for treating bacterial contaminants, if water is boiled properly and sufficiently, it can be up to 98% effective [in treatment of common viruses (like coronavirus, hepatitis, rotavirus), bacteria (like eColi), and protozoa (like giardia or cryptosporidium)] ...(Sari 2019) (NYS DOH) but that's not exctly the whole story, and "boiling" as a term can sometimes be a bit over-simplified.

Watch out:Not everyone understands the importance of "rolling boil" and some start timing their minute when they see a few bubbles appearing in the "boiling" water container. That's a mistake. When you see those "fish eye" bubbles not all of the water has been heated to its boiling point (212°F or 100°C at sea level).

For clear water or water that has been filtered to make it clear, you should bring the water to a rolling boil and keep it rolling for at least one minute. At an altitude above one mile increase the rolling boil time to three minutes.

For example, on boiling time for water in an effort to make it safe to drink,

Watch out: we don't know the quality of the water with which we're starting. In this article series we include material on providing drinking water in emergencies. Around the world that sometimes means starting with water that's not even clear of sediment and debris. Experts have pointed out that in that circumstance it may be appropriate to boil water longer for safety.

It's worth noting that it is not just the temperature to which we raise water in an effort to kill pathogens, but also the duration of time needed at that higher temperature.

Some killing of pathogens in water begins even before the water has reached the boiling point; the "boil for a minute" guideline is generally right but there are plenty of exceptions that argue for longer boiling time or even for the need for other disinfection methods.

• 60.5% of [boiled and then ] stored drinking water samples were positive for TTC, with 22.2% falling into the medium risk category (11–100 TTC/100 mL). (Clasen 2008)
  
  Our findings show that boiling is not an undifferentiated practice, but one with different methods of varying effectiveness, ... (Cohen 2017)
  
  Our results show that the practice of boiling in the study community significantly improves the microbiological quality of water, but does not fully remove the potential risk of waterborne pathogens. (Rosa 2010)
• The non-detection of E.coli does not guarantee that water is safe to drink because a water sample is only a snapshot1,21 of the water being distributed and because some organisms are more resistant to chlorine/disinfectant than the indicator E.coli. (Verhille 3013)
• A small percentage (3%) of the DWAs were do not consume orders which are issued in cases where contaminants that cannot be removed through boiling are present [24]. It is particularly troubling that 14% of the DWAs were long term advisories, in effect for more than one year with some in effect for the entire 10-year study period. This study shows that access to safe drinking water is not reliable within First Nations communities across Ontario; ... (Galway 2016)
• While boiling is scientifically proven to eliminate bacteria, data demonstrate that pragmatics inhibit their total destruction. Furthermore, data and the literature indicate that a range of cultural, economic, and ancillary health factors challenge the uptake of boiling. (Juran 2014)
  

You can see that when we need more time to kill more-persistent pathogens, and if we are bringing our water to the boiling point quickly, the duration of heat-exposure up to the boiling point is reduced, so the total "hot time" is reduced; that's where the "boil it a bit longer if you brought it to a boil quickly" advice originated.

Of course none of the content here is invented out of thin air - we also have cited sources both above on this page and also in the references section.

Thank you for taking time to write - we can use all the editing help we can get. If you can add a couple of citations from your "all the leading health authorities" that would be useful to provide here for other readers.

Oh and on any of our pages at the bottom see additional source citations.

On 2021-04-13 by Anon

This article is full of inconsistencies. The chart says to boil water at sea level for 1 minute. Then it states that "If you are boiling water on an unusually hot powerful heat source, boil it a bit longer to be safe." Then below that it says "Typically, experts recommend three minutes of rolling boiling water at sea level altitude to safely disinfect water for drinking."

The answer given by all the leading health authorities is to boil water for 1 minute at sea level altitude. If you're above 6500ft then add another couple of minutes.

On 2017-02-08 by (mod) - how long to boil clean tap water to make it safe: 1 minute +

@Anonymous,

Tap water in most countries and cities is pretty clean of sediment and debris; in those cases, unless testing has found a specific hard-to-kill pathogen, boiling tap water for a minute (if you're at or close to sea level) will be sufficient.

Keep in mind boiling is only addressing pathogens in drinking water, like bacteria and some cysts. It may do little to remove some chemical contaminants if those are present as well.

On 2017-02-08 by Anonymous

If you're not sure about tap water how long should you boil it .

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Citations & References

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