Boil 3, Add 1 Method

Note that the method described below is only accurate at sea level.

The Boil Five, Add Two Method is a proposed way to pasteurize a given amount of water using less fuel, without the need for a thermometer. To be safe to drink water doesn't have to be boiled (see Water pasteurization); it only has to be heated to 65°C (150°F). If one has a thermometer, then it is very easy to heat water to this lower temperature and know that it is safe to drink. The Boil Five, Add Two Method provides a way add hot and cold water together to be able to pasteurize water when no thermometer is available.

Using this method, one brings five measures of water to a boil and then adds two measures of cold water. Tests show that adding 2 measures of water at 1°C (the coldest temperature where water is still liquid) to 5 measures of boiling water (100°C) will result in 7 measures of water at 70°C (which leaves a margin of error of 5°C since a safe pasteurization temperature is 65°C).

Steps for use

1. Select a small container much smaller than your cooking pot.
2. Do this five times: Fill the container with water and empty the container's contents into the cooking pot.
3. Heat water to boiling.
4. Add two containers full of cold water to the boiling water.
5. The water is now safe to drink.

Things that you should note

• Water boils at a lower temperature at higher altitudes. Thus it may be necessary to add less cold water.
• Add the cold water as soon as the water in the pot boils so that the hotter water isn't reduced in volume by evaporation.

Topics for study

The above method was designed to work even if the colder water is close to freezing. This is necessary since we must design for the worst-case scenario. If there were a way to