When does water become drinking water?

Wann ist Wasser Trinkwasser?

When going for a hike, especially during the hot summer days, it is important to have enough water on you. The only thing that’s laborious, is hiking with all that extra weight and getting it up the hill. You should drink about 5dl per hour, which is 3kg extra luggage on a 6 hour hike. It would be a lot easier if you could just take one bottle and refill that bottle along the hike at fountains, streams and water sources in the mountain.

But how do you know whether the water is clean and doesn’t have any impurities, bacterias or viruses that could cause diseases?


Fountains located in cities or villages in Switzerland that don’t have drinkable water, need to have a sign which clearly declared that the water is not for drinking. However this rule doesn’t apply if the fountain is located on a pasture, in the alps or on private property, since these fountains are for animals. Drinking water from such a fountain can cause diarrhea and vomitting.

Mountain streams / water springs

In general water coming from mountain streams and water springs is clean and drinkable. But how do you know whether it is clean water? Humans produce waste and wherever humans live there is dirt! In addition there are grazing animals who pollute the water as well. Therefore you shouldn’t drink any water where there are grazing animals. In case of an emergency only take water from above the pasture, where the grazing animals can’t pollute the water with their excrations. Never take water below the pasture!

In uninhabited regions, the risk is very low on contaminated water.

Cold vs. warm water

As a rule of thumb, the colder the water the cleaner it is. In warm water, viruses and bacteria feel more comfortable and reproduce much faster. Here too, water is always found above the settlement.

Stream velocity

The faster the flow rate of the water, the better the quality. Dirt and impurities cause the water to flow more slowly. Therefore never drink from standing waters.

Clear vs. murky water

The clearer the water the better, murky water is a playground for viruses and bacteria.

Types of impurities

  • Agricultural such as, for example, fertilizers, pesticides, herbicides, etc.
  • Unresolved particles and sediments
  • Bacteria such as e.g. Escherichia coli (E-coli) or salmonella
  • Viruses such as e.g. Hepatitis A
  • Protozoa, e.g. Giardia

Water treatment

Even if all the above parameters apply, the water may be contaminated. There are various methods, whether for hiking or traveling, to treat contaminated water to drinking water.

Boil the water

Boiling water is a reliable method to kill pathogens. The water is heated to 100C ° in order to kill dangerous organisms, which are differently sensitive. Some of them die above 100C ° and some before 100C °. The water should boil for 3 minutes. At higher altitudes the water has to be boiled longer, as the water has a lower boiling point when the air pressure is lower. The recommended value is 1 minute longer for every 150 meters of height.

Water filter

By means of a water filter, bacteria, single cells and multiple cells can be filtered out of the water, but this does not protect against viruses. Combifilter with active carbon can additionally bind small exciters as well as flavor and smell substances.

Chemical disinfectants

Chemical disinfectants are cheaply available in the outdoor trade, but are only suitable for clear water and require up to 2 hours of exposure time.

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