In Extreme Simplicity: A Guide to Urban Homesteading (Dover Publications, 2013), Christopher and Dolores Lynn Nyerges explain the most practical and inexpensive methods for creating personal water filters for protection from chemical and biological contaminants. The following is an excerpt from Chapter 6, "Water."
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If you ever suspect your water of being contaminated, boiling is the easiest and cheapest way to purify water. Any hobo can pick up an old can and use it to boil water. According to U.S. Forest Service hydrologist Mike McCorison, who is familiar with the water situation in the California forests, boiling kills every living organism that can make us sick. Of course, boiling does not deal with chemical contaminants, merely biological contaminants. Distillation is the only method of purification that purifies water from chemical as well as biological contamination.
Distillation and Purification
Distillation is the best way to purify water, because only pure water distills out. However, distillation setups are generally not portable, nor cheap.
If you already have a kitchen distillation unit, that's good! These devices are sold at appliance stores and are most often used for distilling tap water. However, because most of these run with electricity, a high-tech distiller may be of no use when you need it most urgently. We have seen some low-tech distillers that need only a flame to operate and some that actually work with concentrated light from the sun. We haven't used one of these ourselves, but they are worth investigating.
There are also chemical methods of water purification, such as the pills and tablets you can get at backpacking supply stores, with new products becoming available all the time in this field. We don't claim to know all the products on the market, but we would argue in general that none of the water-purification pills on the market are advisable. Though some of these may be effective when fresh, most people don't use up a whole bottle of water purification pills at one time; instead they save the pills for future use. Once opened and exposed to heat and air, these pills are usually not efficacious beyond a year or two.
Our research indicates that iodine crystals are the cheapest, most efficient, and longest-lasting chemical means of purifying water. While some pills and liquids have a shelf life of up to two years, iodine crystals are effective in a broad variety of water conditions, and they remain viable indefinitely. Iodine-purified water tastes better than chlorinated water but does take some getting used to. However, some people should not use iodine crystals, including pregnant women and anyone who has a thyroid condition, because iodine concentrates in the thyroid.
To purify water using this method, add about 4 grams of USP-grade iodine crystals to a l-ounce glass jar with a plastic lid (Bakelite is best, because iodine water will not degrade this type of plastic). Fill this small glass jar with water and hold it in your hands for a few minutes so that the water remains at body temperature. The water inside the jar will turn a golden color from the iodine crystals. Then, measure out 10 cc of this concentrated iodine liquid and pour that into a quart or liter of water. The water in the bigger container should be safe to drink in about five minutes. We use a lid on our small glass jar that holds a volume of exactly 10 cc, so the lid itself can serve as our measuring device. Keep in mind that you must be careful to pour out 10 cc of the gold-colored liquid and never add the crystals directly to your drinking water, because the crystals themselves are toxic. Once you use up the liquid in the small concentrating glass with the crystals, you simply add more water. You can keep doing this for as long as you have crystals remaining, which could be up to ten years.
Another method of water purification utilizes filters.
There are many filtration-type water purifiers on the market, many of them designed for backpacking, and most are very effective. We use a brand called Timberline, which is a pump filter, quite easy to use. It is made primarily of plastic with a cylindrical filter and retails for about $20. There are others that are more durable and cost a little more, for instance, the one called First Need. The best model, in terms of overall sturdiness and effectiveness, is the Katydyne, a device used by most Red Cross personnel when going into areas where the water purity is questionable. This company manufactures several models, and the one most popular with backpackers will cost you somewhere in the neighborhood of $150 to $200 (depending on where you buy it and whether or not it's on sale).
Water purification straws are another option worth considering. As the name implies, these look like straws, and you simply suck the impure water through the straw, which is supposed to remove impurities. These cost less than $10 and are convenient to use. But we have been told that you should regard these as useful only on a temporary basis, for several days, say; then you should discard them. Trying to save money, people may hold on to these filters after they've used them, but they may not be effective anymore.
It's important to acknowledge that sometimes the unexpected happens: you need to purify water, but you have no purifying devices and you can't make a fire. In such situations—whether they are the result of an urban disaster or a wilderness mishap—it's worthwhile knowing about some of the truly makeshift filters that people have devised over the years.
Cloth Water Filter
If you are not seeking potable-quality water and are simply trying to filter out mud and debris, a clean cotton kerchief will work just fine. Pouring muddy water through the cloth will remove most of the unwanted materials. Moreover, you can just let a container of muddy water set for a few hours and the heavier solids will settle out. If you may be tempted to drink the water you acquire in this way, remember that the simplest and the best basic method to purify water is boiling.
Sand and Charcoal Water Filter
The 1938 Boy Scout Handbook describes an interesting filtration system that can be easily constructed if you have certain basic materials. You need two buckets or barrels (size determined by your needs) connected by a tube or pipe near the bottoms of the containers. Your impure water is poured into the first barrel, which has been filled, from the bottom up, with a perforated plate a few inches up from the bottom (basically, a metal plate or disk with holes in it), a layer of charcoal, a layer of coarse sand, and a layer of gravel. You leave about one-quarter of the space at the top for adding the impure water. The water passes through the layers of materials, then passes through the tube into barrel number two, which is filled, from the bottom up, with a layer of coarse sand (the pipe or tube from the other barrel comes into this coarse sand), charcoal, and gravel. The top third of the second barrel should be left clear for your filtered water.
Such a filter is effective for removing much of the grit and sediment in the water and probably works better than allowing the water to settle. The charcoal may help to remove some pathogens from the water. If you've got on hand the buckets or barrels, tubing, and the materials to put in the barrels and you do not have way to boil water (or cannot have a fire), then this is a low-tech system worth considering.
Peat-Charcoal Water Filter
Here is another low-tech water filter, tested in a lab by Stefan Kallman some twenty years ago when he invented this technique. Kallman's design uses an empty beer or soda can or container of similar size, which can be found just about anywhere, whether in the outback or urban jungle.
Remove the lid from the can and make a few small holes in the bottom. Put a layer of sphagnum moss in the bottom of the can—fresh green sphagnum, recently picked, with most of the water pressed out of it (sphagnum can be bought at garden supply stores or foraged in the eastern United States or Europe). Next grind some charcoal until most of it is fine powder, though a few small chunks are all right. Do not use barbecue charcoal that has any lighter fluid in it; you can make your own charcoal by burning hardwoods in a campfire. Mix the charcoal with peat (foraged or purchased in a garden center). You can also mix in some sphagnum. Blend the three ingredients and pack them into the can until you have filled it about two-thirds full. Then add a layer of small pebbles to the top.
One must carefully pack the materials into the can and then carefully pour suspect water through the filter. The first few pours won't be filtered well yet, and you'll note that the water will initially be grayish with particles from the loose carbon. After a few pours to flush the filter, you will be able to drink the water.
Keep in mind that this filtration method was tested with peat, sphagnum, and charcoal. The charcoal is mostly carbon. Carbon has long been used in various water filters to absorb pathogens. The sphagnum chelates, or chemically traps, some metals and also absorbs some pathogens. The layer of pebbles is also important. Without that, water will tend to form channels in the softer materials below and will pass through without significant filtering.
We have seen many variations of this "primitive" filter, and these are worth investigating. Though it might seem that there are easily available substitutes, we'd caution you to not drink water filtered with other materials until you actually test the resulting water. Our advice is to keep a good, reliable, tested water filter at home, and remember that the easiest and cheapest way to purify suspect water is by boiling it.
Interested in learning more skills in self-reliance? Learn how How to Make a Homemade Solar Oven Out of Cardboard and Aluminum Foil.
This excerpt has been reprinted with permission from Extreme Simplicity: A Guide to Urban Homesteading, by Christopher and Dolores Lynn Nyerges and published by Dover Publishing, 2013. Buy this book from our store: Extreme Simplicity.