How Long Should You Boil Water?
September 19, 2011 by Sergeant Survival
Filed under Survival Guides
Today a friend asked me, ”How long should I boil my water?”. He’s a prepper and a smart guy, but it’s no suprise to me that he’s confused on such a seemingly simple topic. I frequently come upon bad advice on blogs, books and forums about boiling water for purification. It’s something we all need to learn too. Unless you have a treelimb stuck through your leg or a bear staring you down, having enough safe drinking water should be your number one concern.
Unless Your Water Is Toxic, Boiling Water is the Best Method
Boiling kills bacteria, viruses, protozoan’s, and parasites. It does NOT remove chemicals and toxins from the water. Suprisingly not many survivalists cover this side of the conversation. If you’re getting your water out of a perfect mountian stream, then boiling it is probably all you need to do. But if your water source is a large public or private lake or river that collects runoff from cities, then you need a chemical water filter. You’ve got to take the chemicals out of your water before you boil or you will just concentrate them.
Even rain harvested from roofs or plastic lined depressions in the ground may contain some nasty chemicals. Rain can contain a multitude of dangerous chemicals, espeically if you live in or near (read 50+miles) an urban enviroment.
Assuming your water is chemical free, modern filtering devices and the chemical treatment of water are only substitutes for boiling water. The best part is, unlike most survival tecniques, we all know how to boil water and it requires no special tools. This means that boiling water is sustainable, unlike filters and chemical treatment. As long as you have a source of heat and a fireproof vessle of some sort you can boil water.
The Case For A Lid
Whatever pot you use to boil your water in, make sure it has a lid. Boiling water without a lid is a huge waste of resources. Not only is your water evaporating right before your eyes but you are wasting heat as well. Doing something as simple as placing a good fitting lid on your pot can cut the time it takes for your water to boil significantly. Pasteurizing water also works much better with a lid as it traps the heat inside the container for a much longer time.
Commonly Stated Water Boiling Times
I’ve heard so many different amounts of boiling times that it makes my head spin. It sees like most people spout facts based on personal choice with no scientific proof to back it up. Even different government and health organizations cannot agree on a correct time (what a suprise).
The most common stated water boiling times:
- “Boil water for 10 minutes” is what your mama probably told you
- “5-minutes of boiling” is also frequently thrown around
- “Boil the water for 20 minutes”. You gotta be kidding me?
- “A rolling boil for 1 minute”. Getting closer….
- “When at high altitudes you need to boil water for twice as long”. 40 mins?
So which of the above statements are actually true? None!
That’s right. Follow any of the above times and you will waste two of your biggest resources. Water and fuel. Wasting water to evaporation when you’re short on water to begin with is foolish. Whole forests have been cut down for firewood in order to boil drinking water. Weekend hikers and tough mountian men alike have used up the last of their precious fuel to boil water for crazy amounts of time. In a survival situation you cannot afford to waste valuable resources and energy like this
The Correct Water Boiling Time
The correct amount of time to boil water is a whopping 0 minutes. Thats right, zero minutes. None. Nada. Zip. Zero. Read below…
According to the Wilderness Medical Society, water temperatures above 160° F (70° C) kill all pathogens within 30 minutes and above 185° F (85° C) within a few minutes. So in the time it takes for the water to reach the boiling point (212° F or 100° C) from 160° F (70° C), all pathogens will be killed, even at high altitude.
What is not well known is that contaminated water can be pasteurized at temperatures well below boiling, just like milk, which is commonly pasteurized at 160°F (71°C)….
The truth is, with a water temperature of 160 to 165 degrees F (74 C) it takes just half an hour to pasteurize. At 185 degrees this is cut to just a few minutes and by the time water begins to boil at 212 F (100 C) the water is completly safe. I still like to let my water sit in the pot for a minute and cool a bit. This extra time gives the water a little bit longer to pasteurize.
So what about high altitudes? At high altitudes the time it takes for the water to reach a rolling boil and then cool means you can safely drink it. If you live above 2,000- 3,000 ft altitude make sure you let your water sit in the pot (with a lid on it) until it cools before drinking. If you’re making a tea or coffee make sure you let it sit and then reheat it to the desired temperature.
You don’t need a thermometer to measure water temperature either, just take your water to a full boil and then immediatly take it off the heat. Leave the lid on (you do have a lid don’t you?!) By the time it comes to a rolling boil you’ve wasted time, fuel, and water.



