Water Purification

There are many “experts” who say that high-elevation water is usually clean and that treating it is not required. And it is true that the risk of contamination varies from place to place, even within the same water source. However, any water on the planet could be contaminated with microscopic pathogens – so why take a chance with your group? Scout backpackers treat their water before drinking. (The only exception would be in an emergency situation.)

Studies conducted on backcountry water quality and published by REI. Click.

While eliminating bacteria and parasites in mountain water and snow are the purpose of treating water, most intestinal infections on backpacking trips are caused by person-to person-contact. So maintain good hygiene habits by disinfecting your hands with an anti-bacterial lotion (Purell), after all latrine breaks, before eating, and before meal preparation. To guard against infection, do not pass around bags of food for people to help themselves with “dirty hands.” Better to pour the chips, candy, jerky, etc. into each hand (or cup) to avoid contamination

Choosing your water source is the first step in water treatment. Sunlight tends to disinfect water. Therefore, the water with the least amount of pathogens is found in lakes, near the surface. Still water is also preferable to streams because moving water roils up sand and debris. Try not to use water downhill of grazing areas, developed properties, or campsites.

Backpacking groups have to choose between three basic types of water treatment: boiling, chemicals, or filtering. Each has its defenders and detractors. It’s common to have to use multiple methods on the same outing, so be prepared.

Boiling Method
None of the common pathogens can withstand temperatures above 170 degrees. Bringing water to a boil is an effective way to sanitize it for drinking since even at high elevations water will not boil until it is hotter than 200 degrees. Some authorities recommend maintaining a boil for 2 to 5 minutes. While this may not be a convenient method for large amounts of water, or while traveling on the trail, it is a good back-up procedure, and suitable when cooking.

Pros: Doesn’t require expensive equipment. Always available. Effective. Inexpensive.
Cons: Takes a long time. Have to use fuel. End up with hot water (good for cooking, not for drinking).

Chemical Treatment
Chemicals are also an effective method for water treatment. They may take 15 to 30 minutes to disinfect the water (perhaps longer in very cold water) and they do not remove any sediments, but they are lightweight and relatively easy to use. Iodine tablets have been a common chemical treatment, but leave an odd taste to the water, and are not effective against cryptosporidium.

Treatment with chlorine dioxide in liquid form such as Aquamira or Klearwater is more effective than iodine and adds less of a taste to the water. Aquamira comes in two separate bottles that have to be premixed, and has a shelf life of about 4 years. Klearwater comes in a single bottle and is easier to use, but has a much shorter shelf life of only a few months.

Another chemical method (the MSR Miox) is a proprietary treatment that uses a small electric current to create a chemical reaction called electrolysis to disinfect the water.

Pros: Lightweight and easy to pack. Easy to use. Inexpensive.
Cons: Water usually tastes bad (You can add a neutralizer to improve the taste). Not appealing to use with muddy water. Drink mixes can dilute effectiveness. Have to wait until chemicals work before drinking (often 30 minutes).

Filtering – Pump Method
There are many different types of water filters that treat the water by passing it through a very fine filter. Most Scout units have experience with pump filters from market leaders like MSR and Katadyn (although there are many brands). The pumps typically last two/three seasons, but the actual filters that go into the pumps typically have to be replaced every year. (Replacement filters can costs as much as the pump itself.) Backpackers have to find a suitable and comfortable spot, drop an intake hose into the water and place an outflow tube into the nalgene bottle (or anything else) and then pump (and pump and pump and pump).

The hose going into the water is considered contaminated because it comes into direct contact with the water source. The tube going into the water bottle is considered clean and must be handled carefully. If the hose touches the tube (very possible when you are perched on a log fighting for balance while trying to unscrew the top of your water bottle as mosquitoes swarm around your head and arms) then both tubes are contaminated. To be extra careful, you then need to boil the tube or soak it in clean water with a few drops of bleach to sterilize it again. The same is true for water bottles that fall into the lake.

A filter should be capable of straining out particles as small as 0.2 microns. Filters will also sift out sediments and convert cloudy water to clear water. Since filters work by mechanical means they can disinfect water immediately and are a convenient water treatment option. However, filters can become clogged or break. Therefore, a back-up treatment system is usually required. When treating water with a lot of sediment you can pre-treat the water by allowing it to settle and then straining it through a sieve such as a coffee filter or bandana.

Pros: Removes sediment from the water. Provides clean water immediately.
Cons: Expensive. Filters can clog or break. Hard work to filter water for a large group. Easy to contaminate the hoses. Bulky and heavy (11 ounces dry).

Filtering – Gravity Method
Gravity filters are newly introduced and destined to become very popular with Venture Crews and large backpacking groups. Generally they work like this: fill a bag from any water source (two gallons or more), hang the bag in a tree, open a spigot and the water flows through the filter and into your water bottle (or cooking pot) at the rate of a half liter per minute. Easy and no pumping required.

Reviews on the backpacking websites are generally very positive. The Katadyn Base Camp System only weighs 10 ounces (about the same as a pump filter) and doesn’t take much room in your pack. It also uses the same filter as their pump filter products. The following video gives you an idea of how it works.

Water filters generally do not removes viruses. However, viruses are rarely found in North American wilderness waters. Only purifiers (not filters) eliminate viruses. (A purifier is just a filter that strains smaller stuff out of the water and sometimes adds chemicals. Purifiers are commonly used by international travelers.)

Whatever treatment method you use – be meticulous. Threads of water bottles cannot be exposed to untreated water or they need to be cleaned. The ends of filter hoses that discharge clean water need to be kept separated from contaminated components. Everything should be kept clean.

A note about water bottles.
There has been a lot of discussion about standard nalgene brand water bottles because they contained BPA, which was found to have a distant link to cancer. As a result, many young backpackers bought other brands in non-standard shapes and sizes. This diversity has complicated many a backpacking trip because most filtration systems are designed to work with standard wide-mouth bottles. Other sizes can be accommodated, but with varying degrees of difficulty.

My recommendation. Scouts should have two one liter bottles with wide mouths. They put their drink mixes in one and keep the other clean. (Water bottles with drink mix is a smellable and may attract bears. On one of our trips trip a bear actually cracked a nalgene bottle by biting into it to get to the lemonade inside. The bottle should have been in the bear bag, but the Scout forgot!)