How Long Should You Boil Water to Sterilize It And Why?

logo by Editorial Staff | Updated on September 22nd, 2023

Water is indispensable to life. We consume it, cook with it, and use it for sanitation. However, it’s not enough to just have access to water; it needs to be safe and free from harmful elements. The subject of sterilizing water for safe consumption often brings up questions like, “How long should you boil water to sterilize it?” or “Why is this process essential?” In this comprehensive guide, we will explore these and many other important aspects surrounding the sterilization of water. Equipped with this knowledge, you can protect yourself and your loved ones from waterborne illnesses, whether you’re at home or venturing into the great outdoors.

Why Do We Need to Sterilize Drinking Water?

Clean water is a fundamental requirement for a plethora of daily activities ranging from brushing your teeth to cooking your meals. But let’s focus on what happens when you’re left with no choice but to consume water that isn’t adequately sterilized. Drinking untreated water can lead to severe medical conditions such as nausea, diarrhea, and stomach cramps. Even worse, it can expose you to life-threatening diseases like cholera and typhoid.

Boil Water

Common Scenarios Requiring Water Sterilization

  • Adventure trips like hiking or camping in remote areas
  • Residing in an isolated cabin or cottage
  • Traveling to countries with poor water infrastructure
  • Natural disasters that compromise local water supply

In particular situations, like chemical spills or disease outbreaks, boiling water alone won’t suffice. You’ll need additional water purification measures to ensure safety.

Types of Contaminants Found in Water

Before diving into the process of sterilizing water, it’s important to know what we’re up against. Water can contain a variety of pollutants, including:

  • Bacteria: E.g., E. coli, cholera
  • Viruses: E.g., norovirus, hepatitis
  • Parasites: E.g., Giardia, Cryptosporidium
  • Metals: E.g., lead, mercury
  • Chemicals: E.g., pesticides, herbicides
  • Pharmaceuticals: Residual medicines

Of these, only bacteria, viruses, and parasites can be effectively eliminated by boiling. Metals and chemicals need more advanced purification methods.

3 Harmful Organisms Eliminated by Boiling Water

  • Bacteria: Examples include E. coli and cholera, which can lead to severe digestive issues and even fatal illnesses.
  • Viruses: Norovirus and hepatitis are among the viral pathogens that boiling can destroy.
  • Parasites: Boiling effectively kills parasites like Giardia, which can otherwise result in prolonged digestive distress.

The Science Behind Boiling: How Does It Work?

Contrary to popular belief, boiling water doesn’t just kill bacteria; it also sanitizes the objects submerged in it. The reason is that moist heat is an effective sterilizer. However, boiling is not practical for large-scale sterilization like cleaning countertops or utensils due to the risk of burns.

Understanding the Variables: Time, Temperature, and Altitude

When it comes to sterilizing water by boiling, three key variables come into play: time, temperature, and altitude. A rule of thumb is to boil water for about 20 minutes at 100°C (212°F). However, these numbers can change depending on your altitude. At higher altitudes, the boiling point decreases due to reduced atmospheric pressure. This means you’ll need to boil water for a longer period to achieve the same level of sterilization.

Time Required for Sterilization at Different Temperatures

  • 175 Degrees Fahrenheit: More than 30 minutes
  • 212 Degrees Fahrenheit: 20 minutes
  • 250 Degrees Fahrenheit: 15 to 20 minutes

Why Does Sterilization Take Time?

The efficiency of sterilization depends on several factors:

  • Temperature: Higher temperatures expedite boiling and thus, sterilization.
  • Altitude: At higher elevations, water boils at lower temperatures, requiring longer sterilization times.
  • Stubborn Microbes: Some pathogens are resistant and require sustained high heat for elimination.

How to Sterilize Water: Step-by-Step Guide

  • Fill a kettle with water.
  • Heat the water until it reaches a rolling boil (212°F or 100°C).
  • Maintain the boiling state for approximately 20 minutes.
  • Turn off the heat and let the water cool.
  • Once cool, the water is ready for safe consumption, cooking, or even dental hygiene.

Remember, it’s a good idea to boil extra water for other uses, such as washing fruits and vegetables, to save time later.


Whether you’re out camping or dealing with a compromised water supply at home, understanding how to sterilize water is crucial for your health. Boiling is a simple yet effective method to ensure you’re consuming water that’s free from harmful bacteria, viruses, and parasites. By following the guidelines provided in this article, you can reduce the risk of waterborne illnesses and enjoy the peace of mind that comes from knowing your water is safe to drink.


Editorial Staff

Our writers, editors, content managers, and SEO specialist. We all take part in crafting amazing articles. We spend hours ensuring that each article is based on facts, researched, and thorough. You'll never want to click the back button to look for more answers other than here!