How to purify water
The affluent and developed west often takes its clean water for granted. While travelling, water purification and sanitation systems don’t exist in the same way that we know them, and in particular, when climbing, you are responsible for your own water. This is especially important at altitude because staying hydrated is a central preventative method for many altitude related illnesses. If you don’t take the proper precautions the contaminated water can cause illnesses too. Either way, it is vital that you only drink safe water, and it is best to take responsibility for it yourself.
The main parasites which need to be eradicated are the cysts which cause Giardia and amoebic dysentery. Small amounts will not affect them body, but in large numbers these pathogens can take effect. They can survive in cold, even freezing water for several months because of their hard protective shells. Chemicals are generally needed to break through these shells, however boiling the water will automatically kill them.
There are many methods for purifying water and the list below should provide useful information as to which methods to use and when.
Iodine Based Methods
- Iodine tablets – Their active ingredient is tetraglycine hydroperiodide. You should allow 30 minutes rather than the usual 10 if the water is cold, and it is possible to double the dose if the water is cloudy, which denotes more organic material.
- Polar Pure – This is a glass bottle with iodine crystals in, teamed with a filter to prevent the crystals escaping. The temperaturestrip and instructions determine the required dose. This method works by dissolving small amounts of iodine in the water. It is effective and cheap.
- Iodine Solution – One of the most common methods, but the most messy. Another downfall is that the different brands are different concentrations, but without warning. Because of this, and the makeup of the solution you usually end up consuming far more iodine than is really necessary. For a 2% solution use 5 drops per litre of water. Leave to stand for 15 minutes before drinking. If the water is very cold or cloudy then leave it for 30 minutes, or alternatively use double the amount of drops.
Note: If you are pregnant, suffer from a thyroid disease or have an iodene allegy, consult a doctor before using any iodene water disinfection methods.
Chlorine Based Methods
- Super-chlorination. This uses a high dose of chlorine but later neutralises it using hydrogen peroxide, and is very effective.
- Chlorine tablets. Used alone these won’t protect against Giardia. Instead use a fine filter and half a tablet.
There are now so many water filters suitable for altitude on the market that it is almost impossible to give general advice. Make sure to follow manufacturer’s instructions, especially when cleaning. Although effective, many people opt for other methods as filters are bulky and heavy.
Bottle water is heavy, expensive and is unlikely to be as clean as is necessary. This is not a practical option.
The general advice is to boil all water for 5-10 minutes plus 1 minute for every 300m above sea level, up to around 5500m where boiling becomes ineffective. The relationship between time and temperature is inverse when it comes to water disinfection. The higher the temperature, the less time is required. For instance, pasteurising can take place in 30 minutes at 70°C/158°F, while sterilising takes place in 5-10 minutes of boiling at sea level. Here are the boiling temperatures for altitude:
- Sea level: 100°C/212°F
- 5,000ft/1,525m: 95°C/203°F
- 10,000ft/3,050m: 90°C/194°F
- 14,000 ft/4,270: 86°C/187°F
Boiling water will eradicate a good proportion of all parasites and is often the easiest way to purify water, although it should be noted that the hepatitis A virus needs a full minute of boiling to eradicate. Boiling can also be used as a stage prior to other methods for extra precaution. Tea, coffee and hot water are all safe to drink as long as the water has been brought to the boil before drinking.