Chapter 10

Water and Water Purification

Obtaining  Filters vs. Purifiers  Using  Criteria  Comparisons  Vessels  Quotations

TRAVELERS MUST INCREASE water intake as they expend more energy carrying a pack, walking, museum-going, and being outside. In hot climates the need for water doubles or triples. Hikers require a gallon or more per day as they sweat and respire water and water vapor. Note that alcohol and caffeinated drinks have a dehydrating effect.

Thirst is not a reliable indicator of hydration state. As visible semi-mucous membranes, lips are. The next time yours feel dry or chapped drink several glasses of water and see what happens.¹

Another barometer is urine color. If it's always dark you're probably a liter or two low. A rule of thumb is to drink enough water to ensure at least two clear, healthy pees per day.

Obtaining Safe Water

In Western Europe, much of Eastern Europe, and other developed countries you can drink safely from public water supplies. In many (but not all) developing countries the water supply contains diarrhea-producing bacteria. While some hard travelers adjust to impure water over weeks or months, most travelers avoid discomfort by buying most or all of their water.

Ice cubes in developing countries are rarely made from purified water; they bite even from alcoholic drinks.

Buying water

is usually easy. It is sold in convenient one or 1.5-liter plastic bottles which cost from fifty cents to $3, depending on the country. Look for a quality label and a safety-sealed cap. Bottled drinks are also safe and routinely drunk by travelers.

Boiling

makes tea, coffee, and soups safe in developing countries. Opinion varies on how much boiling is necessary, but a minute or two at full boil should do the job.

Iodine

is the preferred chemical treatment for water. It is easy and effective in twenty minutes, but iodine probably should not be used for months at a time. It also should not be used by pregnant women and people with thyroid conditions. The two most popular iodine treatments in the U.S. are Potable Aqua and Polar Pure.

Potable Aqua

consists of tiny iodine tablets in a small glass bottle. Directions are one or two tablets (depending upon temperature, clarity, and Giardia control) per liter of water. Shake and let dissolve, then loosen the cap and shake again to allow the iodized water to spread over the threads, killing germs there. It's ready for drinking in twenty minutes.

The water has a slight brownish-orange color, and a moderate iodine taste. Potable Aqua also comes with ascorbic acid tablets, called P.A. Pure, which greatly reduce the iodine taste and off-color.

Potable Aqua tablets should be left sealed in the glass bottle until use as they have a limited effective life after exposure to air.

Polar Pure

consists of a four-ounce (120 milliliter) glass bottle with crystallized iodine in the bottom. First, the bottle is filled with several ounces of water, then after a few minutes (time dependent on water temperature--a small thermometer is attached) this bottle is poured into a quart of water to be purified. The crystals remain in the original glass bottle. While Polar Pure is slightly more complicated than Potable Aqua, less iodine is used, and it has a longer shelf life.

Liquid iodine

from a dropper bottle is an alternate method used by some travelers. When faced with suspect water in a restaurant they add two or three drops per glass of water, stir, and wait a few minutes. This is unscientific but seems to work.

Silver

water disinfectant tablets are expensive at about $20 for a packet of forty tablets, which purifies forty liters. Silver is an alternative for those who don't want to use iodine.

Chlorine

tablets or liquid are not recommended as a water purifier, as chlorine is unstable and not always effective. Since it is also associated with a small cancer risk, only use chlorine in a pinch.

Filtering

cleans water mechanically. Special purifying filters may make sense when camping away from campgrounds--say in Central American National Parks, or otherwise in the bush. Travelers in Africa, Asia, Latin America, and the former Soviet Union could also benefit. In the long run you could save money by filtering instead of buying, and certainly spare Earth from hundreds of unrecycled plastic bottles.

Boiling is inconvenient since it requires much time and fuel. While iodine renders water bacteriologically safe, it doesn't remove crud or improve taste. A good filter pumps out good water in a few minutes, and provides a real boost as opposed to drinking boiled or iodine-purified--but horrible tasting--water.

Filters vs. Purifiers

Filters work by forcing water through material of a certain pore size which screens contaminants. These are fine for backcountry use in the U.S. and Canada since Giardia is the main contaminant here. (Giardia screening requires a pore size of two microns.) Developing countries, however, may have waterborne viruses, such as hepatitis and polio, which are 0.04 microns or smaller. Thus virus control requires boiling, iodine chemical treatment, or a purifying filter.

The PUR filters listed below, as well as the Sweetwater Guardian with its Viralguard accessory, incorporate iodine matrixes which kill viruses and bacteria without passing much iodine into the water.

According to a Katadyn white paper that appears scientific to this nonscientist, in practice non-purifying filters that screen contaminants to 0.2 microns remove most viruses since viruses usually attach themselves to bigger things, which are then screened. This apparently hasn't impressed real scientists at the EPA, however, so if using a non-purifying filter on suspect developing-world water you probably should add iodine after filtering. While not as much iodine is necessary as with unfiltered water, you still must wait twenty minutes before drinking.

Using Filters

Avoid fast clogging by always using the cleanest available water. If the water is particularly dirty or silt-laden, let it settle in a pot before filtering, and/or use a coffee filter or cloth as a pre-filter. I permanently clogged a not-field-cleanable filter on the second liter drawn from a silty Washington river.

To clean a clogged filter you must carefully follow manufacturer instructions. A grave possibility is contaminating yourself with the nasty bacteria trapped inside the filter. You must also be careful about contamination from the water-source hose. Take care with a ceramic filter since a hairline crack will make it 100% ineffective.

Selection Criteria for Water Filters

If you will be depending on a filter for much of your water field cleanability, pump speed, and ease of use are far more important than a few ounces of weight. A good filter saves you from carrying at least some water, which weighs eight pounds per gallon (or one kilogram per liter). Pump speed lessens the more the filter is used.

Filters with a pore size of one micron or less are good. Smaller pore sizes and smaller filters clog faster. Carbon filters trap pesticides and metals, which for my taste is a worthwhile feature. Ceramic-only filters do not.

For emergency or short periods of developing world backcountry use, filters such as the PUR Voyageur, PUR Scout, and Sweetwater Guardian with iodine cartridge are good choices. If you will be filtering mostly from faucets or sinks (the usual scenario), clogging and pump speed will be less of a problem, so smaller filters should suffice.

If you will be filtering most or all of your water from wells or streams, say in East Africa or the Darien Gap, then you will appreciate having (and essentially require) an easy-pumping, easy-cleaning, full-size filter. You may also require spare cartridges or filtering elements.

A water purifier is not a requirement for developing-world travel. Most travelers buy most of their water and use iodine tablets or drops in a pinch.

Water Filters Compared

All specifications are from the manufacturers--cartridge capacity will be less if pumping brackish or silty water, and after a few gallons of use only Superman can pump as fast as claimed.

Katadyn Pocket

$300, 23 oz. (650 g.). Pumps about one liter per minute. Screens to 0.2 microns. This Swiss product has been widely used for thirty years due to the large and easily cleaned ceramic element, which lasts up to 13,000 gallons (50,000 liters). Because it takes considerable power to pump through thick ceramic, the Katadyn Pocket is best for long term users who may not have access to replacement cartridges, who require high volume and low per gallon cost, and/or tonier musculature.

Sweetwater Guardian Plus

$70, 15 oz. (425 g.). Pumps about one liter per minute. Carbon filter screens to 0.2 microns. Plus model contains an otherwise optional ($25) iodine matrix cartridge for virus protection. Field cleanable. Cartridge capacity rated at 200 gallons (750 liters)--replacements are $30. (Pictured right without hoses or accessories.)

MSR MiniWorks

$60, 16 oz. (450 g.). Pumps about 2/3 liter per minute. Ceramic element with a carbon core that screens to 0.3 microns. While well-regarded like most MSR products and all the filters listed here, for virus removal MSR recommends pre-treating with iodine. Therefore this and the larger WaterWorks II are probably better for long term use if water-borne viruses aren't a worry and iodine is. Field cleanable. Cartridge capacity rated at 40 cleanings--replacements are $30. 

 

PUR Voyageur

$70, 11 oz. (310 g.). Pumps about one liter per minute. Screens to 0.3 microns. Travel version of the popular PUR Hiker that adds virus protection by screening through an iodine resin glassfiber. While the cartridge is guaranteed not to clog for one year, that's mainly a calculation that most purchasers will only use the filter for a few weekends--replacements are $35. 

PUR Scout

$80, 14 oz. (400 g.). Pumps about one liter per minute. Screens to 0.3 microns, then passes through an iodine matrix which kills all other bacteria and viruses. Only a little iodine is absorbed, which can just be detected by taste. An optional (and recommended) carbon cartridge ($15) removes this iodine and many organic chemicals such as pesticides. Field cleanable. Cartridge capacity rated at 100 gallons (378.5 liters)--replacements are $40.

PUR Explorer

$130, 20 oz. (565 g.). Screens to 0.3 microns. Larger and better than the Scout, with faster pumping (about 1.3 liters per minute) and auto-cleaning by twisting the handle. This is probably the fastest pumping, easiest to clean, and with the optional carbon cartridge, most effective filter. Cartridge capacity rated at 100 gallons (378.5 liters)--replacements are $45. (Pictured right with 130 micron prefilter.)

Water Vessels

Plastic water bottle

1 oz. (28.35 g.), free with purified water or soft-drink purchase. Used by most travel backpackers and long distance trail hikers, it's several ounces lighter than other choices, doubles as a pillow, and the screw cap usually works well.

Left to right: The Cube one liter, Nalgene one liter and half liter, and polyethylene one liter.

Nalgene Lexan bottle

4 oz. (110 g.), $6. This is a nearly perfect water vessel. It's beautiful (if you scrape off the advertising); leak proof (due to the stiffness of Lexan); and unlike softer polyethylene, imparts no taste upon water. The negatives are it weighs four ounces, costs money, and makes a terrible pillow.

Polyethylene bottle

3 oz. (85 g.), $4. Cheaper and an ounce lighter than the Nalgene Lexan, but not as leak proof, and it imparts a plastic taste on water.

The Cube

1.5 oz. (43 g.), $2.50. Holds one liter. A convenient water vessel which, when empty, folds upon itself to take up very little pack space. An excellent product. I tuck one away in my pack for occasional extended capacity.

Water Sack

4 oz. (85 g.), $7. Holds three gallons (11 liters) inside two replaceable plastic bags. More convenient than sheep bladders for containing large amounts of water.

Literary Quotations

Then, when the heavens and earth are on fire, and sun drinks up rivers at one draught, when one burnt sienna tone pervades the tawny ground, and the green herb is shrivelled up into black gunpowder, and the rare pale ashy olive-trees are blanched into the livery of the desert; then, when the heat and harshness make even the salamander muleteers swear doubly as they toil along like demons in an ignited salitrose dust--then, indeed, will an Englishman discover that he is made of the same material, only drier, and learn to estimate water.... Richard Ford, England, from Gatherings from Spain, 1846

Notes

1. Due to the principle of homeostasis learned in tenth grade biology, I believe every cell in the body would be functioning in a similarly water-deficient or sufficient manner. back