Disinfecting Your Water

Disinfecting Your Water

By Matthew Stein, P.E., Author of When Technology Fails: A Manual for Self-Reliance and Planetary Survival, ISBN #978-1933392837, published by Chelsea Green Publishing, White River Junction, VT (800) 639-4099  http://www.chelseagreen.com 

Water systems face . . . challenges in some of the new, hard-to-kill bacteria that crop up with growing frequency. Among the most feared is Cryptosporidium, the parasite that polluted Milwaukee's water in 1993, killing 111 people and sickening more than 403,000. It was the worst case of waterborne illness in modern U.S. history. The city's treatment system at the time wasn't good enough to kill the bug, which can evade conventional filters and is resistant to chlorine, most systems' main defense.

-Peter Eisler, “Powerful New Pollutants Imperil Drinking Water Supply,” USA Today, October 12, 1998

Contrary to popular opinion, clear sparkling water is often unsafe for drinking. Even spring water may not be safe. Deep-water springs from gravel or sand sources are usually safe, but may be contaminated by runoff from agricultural fertilizers, septic systems, sewer lines, and so on. Springs emerging from rock crevices can be exit points for underground streams carrying pollutants from far-off sources. When unsure about the source of your water, it is safest to boil, chemically treat, or filter the water through a certified water filter.

Boiling all your daily drinking water is time and energy consuming. Most chemical treatments leave an aftertaste and should be used with care to ensure the proper concentration and contact time for the temperature of application. Chemical treatments, except possibly for the new Aquamira products, do not provide guaranteed protection from Cryptosporidium cysts (common in surface water contaminated by farm animals), which have been found to survive a 24-hour soak in undiluted household bleach! Portable filters can process surface water into potable water, but may not purify as well as their labels lead you to believe. The safest method for portable, fast, reliable water disinfection is a combination of chemical treatment and filtration, though further testing on the Aquamira products may prove that they are reliable chemical treatments for all known microorganisms. Recommended methods for sterilizing and disinfecting water are summarized below.

Heat Sterilization

Water sterilization by boiling is preferred over any method of chemical disinfection. This time-honored method is safe and a sure thing, because disease-causing microorganisms cannot survive the heat of a sterilizing boil. The CDC (Centers for Disease Control and Prevention) recommend that you boil water at a vigorous rolling boil for at least one minute at sea level. At altitudes above 6,000 feet, they recommend three minutes of rolling boil, since water boils at lower temperatures as the altitude increases. Some references (Wilkerson 1992, 71) state that, regardless of elevation, the boiling temperature and the time to reach that temperature are sufficient to kill all pathogenic organisms (milk is pasteurized at 160˚F). Boiled water can be used after cooling (do not add ice).

Note: Boiling usually has no impact on chemical or radioactive pollutants, which must be dealt with by other methods.

Chemical Sterilization

Various forms of chlorine and iodine chemical treatments are commonly used to disinfect drinking water. Chlorination is the most common method of chemically disinfecting water because it is easy to apply, readily available, and inexpensive. Chemical treatments usually leave an aftertaste that some people may find unpleasant. The taste is caused by traces of chlorine or iodine, which are active halogens that can cause harmful health effects over long periods of time.

CAUTION: Except for possibly the chlorine dioxide solutions (tradename Aquamira), neither chlorine nor iodine disinfection is effective against Cryptosporidium cysts. However, all cysts are easily removed by filters that are rated for cyst or bacteria removal.

If treated water has a strong chlorine or iodine taste, you can improve the taste by allowing the water to stand exposed to the air for a few hours, by pouring it back and forth several times between containers, adding a pinch of salt, or by adding some lemon juice. A pinch of powdered vitamin C (available at health food stores) in a quart of treated water will react with free chlorine or iodine and totally remove the bad taste. Running the water through an activated carbon filter will also remove free chlorine, iodine, and bad tastes.

CAUTION: Do not remove free chlorine or iodine until the water has set for the proper sterilization time (see the following table) and do not remove traces of chlorine or iodine from water that is to be stored for long periods of time.

Chlorine Bleach

Liquid chlorine bleaches, such as Purex and Clorox, contain a chlorine compound in solution that will effectively disinfect water. There are some products on the market sold as “bleach” for laundry use that do not contain chlorine and could be harmful. Read the label! The procedure for disinfecting drinking water is usually written on the labels of Purex and Clorox brand chlorine bleaches. When the procedure is not given, one should use the percentage of available chlorine as a guide (see the following table). Chlorine bleach is not as stable and reliable as the recommended iodine treatments. Chlorine is very pH sensitive and alkaline waters significantly reduce its antimicrobial effectiveness (Wilkerson 1992, 72).

Caution: Do not use powdered bleach or bleach with conditioning additives, scents, or colorfast additives.

To purify, add 4 drops of standard liquid chlorine bleach (5% concentration) per quart of water (or about ¼ teaspoon per gallon), and double that amount for turbid or colored water. The treated water should be mixed thoroughly and allowed to stand for 30 minutes. The water should have a slight chlorine odor. If it doesn't, repeat the dosage and allow it to stand for an additional 15 minutes. The slight chlorine taste of treated water is additional evidence of safety. Chlorine bleach loses strength over time, so if your bleach is over one year old, the amount used to disinfect should be doubled.

Chlorine Dioxide

With the discovery that Cryptosporidium cysts pose a significant health threat and often survive traditional chlorine water disinfection treatments, many municipalities have included chlorine dioxide in their water treatment process. Much like ozone water treatments, chlorine dioxide is a powerful oxidizing agent that can kill Cryptosporidium cysts and rapidly purify water. It does not leave the active halogen of free chlorine in the water, so it makes for better tasting water (no aftertaste) than water treated with traditional chlorination.

The Aquamira kit ($12.95) is the first portable water treatment product to utilize chlorine dioxide and will treat up to 30 gallons per kit. Preliminary tests indicate that it may be effective against Cryptosporidium cysts, but it has not yet received EPA purification certification.

Chlorine Tablets

Chlorine tablets containing the necessary dosage for drinking water disinfection can be purchased in a commercially prepared form. Sources for chlorine disinfection tablets are sporting goods stores, army surplus stores, backpacking stores, preparedness/survival suppliers, and so on. Tablets should be used as stated on the instructions. Chlorine tablets can be stored for years. Their small size and precisely measured amount of chlorine in each tablet make them convenient, accurate, and easy to use. For disinfecting large quantities of water, their cost may be prohibitive, but they are a lot lighter and easier to carry than gallons of pure water.

Redi Chlor tablets, from Continental Technologies, are premeasured tablets of calcium hypochlorite that are handy for disinfecting significant quantities of drinking water. Each tablet treats 5 gallons of water, so a single bottle of 100 tablets treats 500 gallons of water for about $19.95, which is far cheaper than the per gallon cost of purifying filters.

Granular Calcium Hypochlorite

Granular calcium hypochlorite is used for chlorinating swimming pools and fairly large quantities of water, and for making stock disinfectant solution. It is best stored in a garage or storage building far enough away from other products that it will not cause pitting and corrosion. Granular calcium hypochlorite is packaged for sale in plastic bottles or drums. Sources of calcium hypochlorite are hardware stores, sporting goods stores, pharmacies, chemical suppliers, and swimming pool supply companies.

Caution: This chemical is poisonous and extremely corrosive.

To make a disinfecting solution, dissolve 1 heaping teaspoon of granular calcium hypochlorite (about 1/4 ounce) for each two gallons of water. This will yield a concentrated chlorine solution of approximately 500 milligrams per liter. To sterilize water, add this chlorine solution in the ratio of 1 part chlorine solution to 100 parts of water to be disinfected (Le Baron 1998, 115). This is roughly equal to adding one pint (16 ounces) of concentrated chlorine solution to each 12.5 gallons of water. If this seems unnecessarily complicated, use the Redi Chlor tablets as described under “Chlorine Tablets”.

Iodine Disinfection

Iodine is one of the best and most dependable germicides and is widely used as a skin disinfectant for the treatment of superficial wounds. You can use iodine to disinfect your drinking water, and it is commonly impregnated into modern water filter media to kill bacteria and viruses inside water filters. However, iodine is not effective against Cryptosporidium cysts. Iodine-treated water has a peculiar odor and taste that some people find unpleasant.

CAUTION: Pregnant or nursing women, or people with thyroid problems, should not ingest iodine-treated water. The EPA recommends that devices which add iodine to the water should not be used for periods extending beyond 2 to 3 weeks at a time.

Tincture of Iodine

Eight drops of 2% tincture of iodine (Salvato 1982, 372) can be used to disinfect 1 quart of clear water (8 milligrams per liter dose). Allow water to stand at least 30 minutes before it is used. Studies of the usefulness of elemental iodine show it to be a good disinfectant over a pH range of 3 to 8. It is effective against enteric bacteria, amoebic cysts, Cerariae, Leptospira, and viruses within 30 minutes.

Iodine Tablets

The use of tetraglycine hydroperiodide tablets is an effective method of disinfecting small quantities of water. Tetraglycine hydroperiodide tablets sell under the brandnames of Globaline, Portable-Agua, and Coghland's. Iodine tablets are handy, compact, and light. The tablets are very effective as a water disinfectant if directions are correctly followed. If the water to be treated is cloudy, it should be filtered, or treated with double the number of iodine tablets.

You can purchase Portable-Agua with vitamin C-based taste neutralizer tablets to totally eliminate the iodine aftertaste. Tablets can be purchased from pharmacies, preparedness/survival suppliers, and sporting goods stores. Once opened, iodine tablets have a shelf life of up to one year.

Iodine Crystal Solution

You can purchase a handy, ready-made iodine crystal water treatment kit from Polar Pure (includes crystals and bottle with thermometer), or you can make your own iodine crystal solution with about 5 g (1/5 ounce) of iodine crystals and a 2-ounce glass bottle. The Polar Pure kit treats about 500 gallons of water for about $10. Cover the crystals with a small amount of water to preserve them from evaporation (sublimation).

When you are ready to use the iodine solution, fill the 2-ounce prescription bottle with water, put the cap on, and shake the bottle for several minutes. Let the heavy crystals settle, then carefully pour out approximately 3 tablespoons (almost all the solution) into 1 gallon of clear water. Use only the iodine solution: leave the crystals in the bottle. Stir the water, and let it stand for approximately 30 minutes. If the water is very cold, let it stand for 1 hour.

You can use the crystals up to about 300 times before they completely dissolve. Be sure to label the bottle with “Poison” and keep it out of reach of children. Elemental iodine is poisonous by ingestion (in concentrated form). Elemental iodine crystals are inexpensive and can be obtained at pharmacies and chemical supply companies.



Disinfection techniques and halogen doses

(All doses added to 1 quart of water)

Sterilization technique

Qty for 4 PPM (parts per million)

Qty for 8 PPM (parts per million)

Iodine tabs (tetraglycine hydroperiodide; Potable-Agua and Globaline products)

1/2 tab

1 tab

2% iodine solution (tincture)

5 drops (0.2 ml)

10 drops (0.4 ml)

10% povidone-iodine solution

8 drops (0.35 ml)

16 drops (0.70 ml)

Saturated iodine crystals in water (Polar Pure product)

2-1/2 t. (13 ml)

5 t. (26 ml)

Saturated iodine crystals in alcohol

2 drops (0.1 ml)

4 drops (0.2 ml)

Household bleach (sodium hypochlorite)

5% 2 drops (0.1 ml)

4 drops (0.2 ml)

Halogen concentration

Sterilization time in minutes at various water temperatures

41 F (50C)

59 F (150C)

86 F (300C)

2ppm

240

180

60

4ppm

180

60

45

8ppm

60

30

15

Note: Recent data indicate that very cold water requires prolonged contact time with iodine or chlorine to kill Giardia cysts (both disinfectants are ineffective against Cryptosporidium cysts). These contact times in cold water have been extended from the usual recommendations to account for this and for the uncertainty of residual concentration.

Source: Adapted from the Wilderness Medical Society Practice Guidelines for Wilderness Emergency Care, 1995.

The methods in the above table have been carefully researched, and are time tested and effective. They are safe when the directions are correctly followed. The raw materials used in purification are inexpensive, but they are poisonous in concentrated form. Use caution and keep them out of reach of children.

Portable Water Filters

There are many different portable water filters on the market. A filter is called a “purifier” if it is certified to remove protozoa, bacteria, and viruses. Other certified filters may remove only bacteria or perhaps just cysts. Many home water filters will remove unpleasant tastes and odors, but will not remove microorganisms. Read the label, but realize that not all similarly rated filters perform the same, nor do all filter manufacturers perform the same tests in the same manner. You can tell if a filter's pump is working or if the filter is clogged, but you can't tell if the filter itself is working effectively against organisms. Actual lab tests to verify microbiological filter function are expensive and there is no thorough testing protocol to ensure that all filters are tested in a standardized way by any lab that does the testing. Having personally designed medical IV filters, consumer water filters, and commercial filtration systems, I will give you my opinion and recommendations, but even I find it hard to sort through the different manufacturers' claims for an accurate filter comparison. For more information on this subject, there is an excellent article by Dan Vorhis, “Portable Water Filters: A Designer's Perspective,” available on the Marathon Ceramics web site at www.marathonceramics.com.

Purifying Filters

Almost any backcountry filter, including those not given a “purifier” rating, will do a good job of removing protozoa and their cysts, like Giardia and Cryptosporidium. Most “purifying” filters have iodine-impregnated resin beads in the filter media, which release iodine into the water to kill viruses and bacteria. These chemically active resins require sufficiently warm water temperatures and contact time to kill bacteria and viruses. Some lab tests indicate that most or all iodine-based purifiers may not pass the EPA “purifier” standard without pumping water through the device more than once or at extremely slow flow rates (Vorhis 1997, 13). If viral contamination is a big concern, I personally would not trust the iodine resin in my purifying filter, but would pretreat the water with a chemical treatment then run it through my filter to remove protozoan cysts and the bad taste of the chemicals. There is one certified purifying filter, the First Need Deluxe Purifier, which uses no iodine to remove bacteria and viruses, and is not as prone to the temperature, flow rate, and usage factors that might allow viruses to slip through most other purifiers.

The new sports bottle type filters are inexpensive, simple, and effective against Giardia, and some are certified purifiers. They are extremely simple, using the squeeze bottle as the pump to drive water through the filter. I would exercise extreme caution using any of these filters to purify water from an urban or agricultural area or for treating brackish or foul-smelling water. If you do use a certified “purifying” water filter on these kinds of water, without secondary chemical treatment, I would be extra careful to run the water through the filters at a very slow rate and run water through the filter twice. PUR, First Need, and Sweetwater make certified “purifying” filters, which cost on the order of $65 to $130, and have fairly low capacities (on the order of 10 to 20 gallons, if you are treating reasonably clear, clean water).

Ceramic versus Carbon Cartridge Filters

If you might use your backcountry water filter a lot, I would recommend that you purchase a filter with a ceramic filter element, like the Katadyn or MSR units. These units offer far longer life at a much lower cost per filtered gallon than carbon-based or pleated-membrane filter elements. All filter elements have clogging problems that will severely reduce their capacity (useful life), if used with dirty water. Ceramic cartridges will clog faster than the other types of cartridges, but can be serviced fairly easily to remove the outer clogging layer and restore the filter to near its original performance. Some filters have replaceable prefilters, which help somewhat with clogging, but since the pore size of the prefilter is usually much larger then the pore size of the main filter, small particles tend to slip through the prefilter and continue to clog the main filter. Backwashing capabilities can also help extend filter life.

Filters generally work on two principles. The first principle is called “sieving.” Sieving is the same as straining particles out through holes in a screen. If the particle is too big to fit through the hole, it doesn't pass through the screen. In addition, most filter media are very thick and create a tortuous path that strains out particles much smaller than the average pore size. Ceramic filter media and most filter membranes work primarily on the principle of sieving.

The second filter principle is called “adsorption.” When a particle sticks to the filter media, the way iron filings stick to a magnet, the process is called adsorption. All filters use a combination of sieving and adsorption, but activated carbon filter media are heavy on the adsorption side. Activated carbon has millions of tiny nooks and crannies. A teaspoon of activated carbon has an adsorption surface area about equal to the size of a football field, making it an excellent adsorption material. Carbon is great for sucking up pesticides, iodine, and organic compounds that tend to give water a bad taste. After a while, the sticky adsorptive surfaces of the activated carbon get filled up, so the filter stops removing bad tastes, chemicals, and odors.

My Filter Recommendations

There are lots of filters on the market. In this section I provide my opinions on quality filters to help you decide what to buy. See backcountry specialty stores or preparedness/survival suppliers for the best selection of portable water filters.

NOTE: Most filter manufacturers rate their filter life with an “up to” gallon rating based on use with very clean water. Unless you know that you will only use your backcountry water filter with extremely clean water, figure on a realistic life of roughly one third the manufacturer's rated life. Sad, but field tests show that this is generally true.

Occasional or Emergency Use

For simplicity, one of the certified purifiers (PUR, First Need, Sweetwater, etc.) would be a good choice. Independent tests of several different filters indicate that the PUR Explorer, PUR Scout, General Ecology's First Need, and the Sweetwater Guardian (with Viral Guard and Siltstopper) all functioned well at removing bacteria, but the PUR models clogged considerably faster than the Sweetwater and First Need models in actual use.

If viral contamination is a major concern, I would not rely solely on the iodine resin in most purifying filters, but would pretreat the water with a chemical treatment, then run it through the purifier to remove protozoa cysts and the bad taste of chemical treatment. Of course, if you are going to do this, you might as well buy a cheaper, longer-lasting filter and treat the water with chemicals.

I would buy one or two of the sports bottle type filters as a backup in case the pump on the main filter breaks. Also stock at least one spare cartridge, since the cartridges clog quickly with dirty water.

Significant Use, Portable

I would definitely recommend a filter with a cleanable ceramic cartridge, such as the Katadyn Pocket Filter ($250), Katadyn Combi Filter ($220), Katadyn Minifilter ($90), MSR MiniWorks ($60), MSR WaterWorks II ($130), or the Marathon e-water ($34.95) which is a small, pumpless siphon filter.

For reduction of bacteria, tests indicate that the MSR WaterWorks II and the Katadyn Combi Filter perform the best out of the longer-lasting portable filters. Test users liked the Katadyn Pocket Filter and the MSR MiniWorks best for simplicity and ease of use and service. After testing numerous models, the U.S. Marine Corps selected the MSR MiniWorks for use by its Amphibious Raids and Reconnaissance Division. Katadyn has been the Third World traveler's standard for many years, but MSR is giving Katadyn a lot of competition.

The MSR units and the Katadyn Combi Filter have the benefit of activated carbon, which will help remove chemicals, bad tastes, and unpleasant odors until the carbon is used up (the ceramic filter element should continue to provide bacterial and protozoa protection long after the carbon is spent).

Even though these units remove around 99% of most viruses, they are not rated as purifiers, so you should chemically treat your water before running it through one of these filters whenever viruses are a concern.

Heavy Usage, Not So Portable

If I wanted to provide purified water for several people over a significant period of time, I would buy one of the recommended gravity-fed units. The per-gallon cost of these units is a fraction of the cost per gallon of using a small portable pump purifier, plus you do not have to sit there and pump away for long periods of time to provide a large quantity of purified water.

Gravity-fed units either have a top reservoir that holds the source water while it slowly percolates through the filter media into the bottom reservoir of purified water, or they are siphon-type units designed to siphon water from one container to another. Gravity-fed units require no pumping but cannot produce water nearly as fast as the recommended high-volume, pump-type unit.

Where viruses are a concern, you should chemically treat your water before running it through one of these filters.

Recommended gravity-fed units are the British Berkefeld, the Katadyn Drip Filter, the AquaRain model 200 and model 400 filters, and the Marathon Ceramics siphon units. The big British Berkefeld filter ($280) has a rated capacity of up to 30 gallons per day and a life of up to 60,000 gallons. It comes with a silver-impregnated activated carbon cartridge for removing chemicals and bad taste and odor.

The Katadyn Drip Filter ($275) has a rated capacity of up to 12 gallons per day and a life of up to 26,000 gallons. It does not have any carbon.

The AquaRain models use state-of-the-art, award-winning ceramic cartridges from Marathon (MSR subsidiary) and contain replaceable silver-impregnated activated carbon cartridges for removing chemicals, taste, and odor. AquaRain model 200 ($199) has a rated capacity of 12 to 15 gallons per day and a life of many thousands of gallons. Their model 400 ($260) has twice as many filter elements and can process 24 to 30 gallons per day. The complete AquaRain unit has not been through EPA purifier certification; however, the Marathon ceramic elements used in the AquaRain unit have been thoroughly tested, indicating an excellent microbiological performance.

NOTE: Filter life is dependent on water quality, filter surface area, filter thickness, and ceramic hardness. In actual use, the large-capacity Berkefeld and AquaRain model 400 will probably have about double the useful life of the smaller Berkefeld, the AquaRain model 200, and the Katadyn unit.

The Marathon e-water siphon filter (list $34.95) has a rated capacity of up to 250 gallons of water. The Marathon Group Siphon filter (list $1,500) will filter 1 to 2 quarts per minute with a capacity of up to 16,000 gallons.

The recommended pump type unit is the pricey Katadyn Expedition ($850), which will pump about one gallon per minute (much faster than the gravity-fed units) and has a rated life of 26,000 gallons. Gravity-fed units are considerably less expensive than pump units with equivalent lifetime capacities.

Preserving Water

Using Silver to Preserve Water

Improperly stored water quickly grows bacteria, which may have effects ranging from unpleasant to life threatening. In the industrialized nations, our digestive tracts have grown accustomed to water sources free of harmful bacteria. As a result, most of us do not have built-in immunities to common local bacteria, which quickly reproduce in untreated stagnant reservoirs. Many a traveler to Mexico has suffered a bout of Montezuma's revenge, often introduced through seemingly harmless ice cubes made from the local water.

The ancients knew about the antibacterial properties of silver. Alexander the Great used silver urns to store water for his troops on extended sea journeys. The ancients didn't know anything about bacteria, but they knew that drinking “old water” could make them sick, unless it was stored with silver. Solid silver will not usually disinfect water, but putting some of grandma's old silverware or some silver jewelry into a storage container is a good way to prevent the growth of potentially harmful bacteria over long periods of time. The silver introduces metal ions into the water that retard or prohibit bacterial growth. Katadyn makes a variety of commercial silver nitrate products (tradename Micropur) for preserving stored water with silver. There are several nonsilver water preservatives, such as “Aerobic 07,” for preventing bacterial growth in long-term stored containers of water. See preparedness/survival and surplus stores for these products. Silver-based water purification products are available in Europe, but these are not approved for use in the United States.

You can make your own colloidal silver solution for preserving your water if you have a colloidal silver generator (see chapter 9). The Environmental Protection Agency has set a limit for the silver introduced into drinking water by bacteriostatic silver-impregnated filters at 50 micrograms per liter (equal to 0.05 parts per million). At this level of silver concentration, several different tests have indicated that silver is only partially effective over periods of time (greater than one hour) against certain bacteria and has little effect against viruses. To obtain these concentrations, you would dilute a 5 part per million (PPM) colloidal silver solution 100:1 with the water to be preserved.

High concentrations of silver, on the order of 5 PPM, might properly purify clear water, but I have no data to support this premise and these concentrations are well beyond the EPA limit. To be safe, I would stick with one of the proven technologies over silver for purifying my water. If I had only a colloidal silver generator, I would definitely use it, but I would use fairly high concentrations of silver and would let the water sit for at least an hour before drinking.

Treating and Finding Water the Low-Tech Way

With a few simple materials, if you can dig your way to moist soil or find some healthy green bushes, you should be able to provide yourself with drinking water.

Treating Water

Slow Sand Filters

You can use a slow sand filter to clean and partially purify your drinking water. Sand filtering is probably the oldest public water treatment method. Filtering water through 3 to 5 feet of sand will remove many microorganisms (like Giardia and Cryptosporidium), most debris, and most radioactive fallout.

As a sand filter ages, a gelatinous layer forms in the upper layer. The gelatinous layer contains many bacteria, which do most of the processing and filtering. These friendly bacteria will destroy many harmful bacteria, though some harmful bacteria, like Salmonella paratyhi, can travel quite a distance through sand filters. The top layer of your sand filter must be cleaned off and replaced regularly.

While sand filters are not as reliable as chemical treatment, they are often incorporated into the primary stages of modern commercial water treatment systems, prior to chemical treatment. One or two layers of charcoal can be included in your sand filter if bad taste, odor, or solvents and other organic chemical contamination is a problem.

CAUTION: Many industrial chemicals and other toxic pollutants will not be removed by sand filters.



 

Figure 5-1. Slow sand filter reservoir.

Tips on Creating a Sand Filter

If you have sandy soil near a lake or river, you can utilize this soil to partially filter the water from the lake or river. If you can, it is best to boil, filter, or chemically treat the water from your sand filter reservoir.

For fresh water, you can dig a trench 5 to10 feet from the water's edge. For salt water, the trench should be about 100 feet from shore. Filtered water will gradually seep into your trench.

If you have access to power and modern materials, you can use gravel, drainpipe, sand, and a pump to make a slow sand-filtered water supply (see Figure 5-1). If you have access to a wheelbarrow, it is preferable to wash the sand prior to loading it into your filter bed. Place a few buckets of sand into the wheelbarrow and fill it with water. Swirl the sand and water mixture, and pour off the muddy water. What remains is relatively clean sand.

You can also filter wet and muddy earth through layers of cloth into a suitable catch basin (see Figure 5-2) to collect water from wet earth. Let the water sit for a while to settle out some of the silt.

Figure 5-2. Crude sand filter.

Charcoal Filters

You can make your own crude charcoal filters to remove bad tastes, odors, and some pollutants such as organic toxic chemicals and radioactive fallout. The easiest way to make charcoal is to burn some wood and pick the bigger partially burned chunks out of the fire. Place these chunks into a 5-gallon bucket and pour the water to be treated into the bucket. Shake vigorously for a few seconds then allow to stand for several minutes before filtering this water through a cloth, sand filter, or coffee filter back into a suitable container. If toxic organic chemicals or radioactive fallout are significant concerns, you should filter your water through at least 3 to 5 feet of sand including two 3-inch thick layers of charcoal. A 50-gallon drum filled with sand and charcoal layers, with a few holes punched in the bottom, could do the job nicely. If you crush the charcoal with some rocks, it will do a better job of filtering.

A more efficient way to make charcoal is with an old-fashioned charcoal kiln, which bakes wood in a closed chamber above a fire. This process makes charcoal without burning the wood sealed into in the upper part of the kiln, since that section of the kiln does not allow enough oxygen flow to support combustion. Another traditional method for making charcoal is by first covering a huge pile of wood with a layer of straw or pine needles followed by a thick layer of dirt, leaving a small chimney flue in the top center. Vent holes were scratched into the sides of the dirt and the pine needles or straw were ignited through these vent holes. The chimney and vent holes were partially covered to control the amount of air to insure that the wood charred into charcoal rather than burn into ash. The charcoal mound was watched carefully for several days then the chimney and vent holes were completely plugged for several more until the mound cooled down. If the mound keeper was not careful, the pile would build into a roaring fire and burn all the wood to ashes.  (Wigginton 1979, 97-99)

If the need should ever arise, common household ion-exchange type water softeners and carbon or slow sand filters are particularly effective at removing radioactive materials from contaminated water sources.

Solar Still

Under a survival situation in dry climates, you can provide yourself with small quantities of pure water with a homemade solar still, using a clear sheet of plastic and a container to catch dripping water. Dig a hole in the ground in an area with wet or moist soil that is also directly exposed to the sun. If the soil is very wet or damp, you may only have to dig a couple of feet. Place a pail or other catch basin in the center of your pit. If you do not have a container, a piece of plastic or waterproof material covering a depression in the earth will suffice. Cover the pit with the sheet of clear plastic and seal the edges of the sheeting with more soil or rocks (see Figure 5-3). Weight the center of the sheeting with a stick, stone, or some dirt.

The sun's rays passing through the plastic sheet will warm the earth, evaporating water from the moist soil. This water vapor rises until it hits the plastic sheeting, which is cooled by the outside air, causing the water vapor to condense and run down the inside of the sheet until it drips off the low point into the container.

Plant Water Pump and Still

A variation on the solar still, this technique uses a living plant as a pump to gather water from under the ground with its roots. You must have a plastic bag or tarp to wrap around a leafy, healthy green plant. Pick a plant that is not too big for your tarp. Dig a small hole on one side of the plant. Wrap your bag or tarp around the plant, lining the shallow hole with the bag or tarp. Tie your bag around the base of the plant and arrange the tarp so that condensing water will trickle down the inside of the tarp and collect in the hole (see Figure 5-4).

Water vapor evaporating off the plant's leaves will condense on the inside of your covering and provide you with a source of water.

CAution: If the plant receives too much sun for too long, it will cook and die under your plastic cover.


Figure 5-4. Plant water pump and still.

Traditional Water Distillation

All kinds of water, from brackish to recycled urine, can be purified with a simple distillation process. Distillation uses a significant amount of energy, because it requires boiling water in one container, capturing the water vapor, and transporting that vapor to a cooler enclosed container where it condenses back into liquid.


Figure 5-5. Water distillation.

“Holy Water”

For countless centuries, holy men, priests, and shamans have engaged in the practice of “blessing the water.” Perhaps there is more to this than we would care to admit or believe? If I had nothing else with which to treat my water, I would take a moment to invite the Holy Spirit (or other spiritual power that you feel comfortable with) to bless and purify my water before I drank it (please use tried and true purification methods when available!!). Leah told me the following story about drinking “blessed water.”

Leah had grown up in a farming community somewhere in California's Central Valley. The water on her farm was terrible. Between the odor and the taste, it made you gag to drink it, so all the local residents relied on bottled water for drinking. Leah had been learning spiritual healing techniques in a class. As one of the recommended class exercises, she had filled a large jug with tap water and placed it by the entrance to their front door. Each time she entered or left the house, Leah would place her hand over the jug of tap water and say a short prayer, asking the Holy Spirit to bless the water.

One day, Leah's brother was terribly ill. He had a very high fever that left his throat parched. At the time, Leah was out of the house, so her niece was attending to the sick brother. He cried out for a drink of water, but the niece could not find any bottled water in the house. Desperate for water, she remembered the jug sitting by the front door. She fetched a glass of water from the jug and gave it to her uncle to drink. The uncle eagerly gulped the water, thanked the niece, and promptly fell into a deep sleep. The next morning, he awoke feeling totally well and amazingly fit. He asked the niece where she had found that water, saying that it was “the sweetest tasting water that I have ever drunk.” She replied that he had drunk water from the jug by the front door.

Knowing that this jug contained local tap water, Leah's brother found it hard to believe that the water he drank could have come from that jug. The niece fetched the jug. When he tasted it, he knew it was the same sweet water he had drunk the night before. They asked the local Culligan representative if the taste of their tap water would be improved while standing in a jug for a couple of weeks. The expert replied that they could put their tap water in a jug for years and it would still taste terrible without being run through a special filter to remove several minerals.