Quick Answer
At higher elevations, water boils at a lower temperature, which means it takes longer to reach a rolling boil. This affects the time it takes to purify water using boiling methods. The exact time will depend on the elevation and the desired level of purification.
Understanding Boiling Point Elevation
At higher elevations, the atmospheric pressure decreases, causing the boiling point of water to drop. This is known as the boiling point elevation (BPE) effect. For every 1,000 feet (305 meters) of elevation gain, the boiling point of water decreases by approximately 1 degree Fahrenheit (0.56 degrees Celsius). At 5,000 feet (1,524 meters), water boils at 198.4°F (92.4°C), which is 2.4°F (1.3°C) lower than sea level. This means that boiling water at high elevations can take significantly longer to reach a rolling boil.
Boiling Time and Purification
To purify water using boiling methods, it’s essential to maintain a rolling boil for at least 1-3 minutes, depending on the contaminants present in the water. At high elevations, this can take longer, typically 3-5 minutes. For example, at 5,000 feet (1,524 meters), it may take around 5-6 minutes to boil water to a rolling boil, while at 10,000 feet (3,048 meters), it can take up to 8-10 minutes. To account for these variations, it’s recommended to use a thermometer to monitor the water temperature and adjust the boiling time accordingly.
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