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"You don't miss your water until your well runs dry"
Y2K Preparedness for Possible Water Supply Disruptions
by Ingrid Schulze

(This paper is distributed courtesy of NOVA Y2K and Ingrid Shulze. It may be copied and distributed freely as long as it is printed in its entirety and no fee is charged)

Y2K and Our Water Supply

In the United States, we often take clean water for granted, and open the tap with little or no regard for the preciousness of this resource.  Hurricanes, earthquakes, floods and ice storms can all disrupt public water supplies. Water supplies are also vulnerable to disruptions stemming from the Year 2000 computer problem. 

The Y2K problem has the potential to affect drinking water supplies internally at the water treatment plant through failures of computers, software or embedded computer systems that control pumps, filtration systems, treatment and disinfection processes, and aerators. Water facilities are also vulnerable to failures of personal computers and software packages, customer billing and materials tracking systems, and a host of embedded systems other than those that directly control water treatment and supply (for example, internal telecommunications equipment, building HVAC and security systems, automated sampling and analytical equipment).Each drinking water supplier has a unique mix of computer systems on which it is dependent. Approximately 30% of all programmable logic controllers with date functions at water and wastewater facilities have some type of Y2K compliance issue.facilities are also vulnerable to failures of personal computers and software packages, customer billing and materials tracking systems, and a host of embedded systems other than those that directly control water treatment and supply (for example, internal telecommunications equipment, building HVAC and security systems, automated sampling and analytical equipment).Each drinking water supplier has a unique mix of computer systems on which it is dependent. Approximately 30% of all programmable logic controllers with date functions at water and wastewater facilities have some type of Y2K compliance issue... are also vulnerable to failures of personal computers and software packages, customer billing and materials tracking systems, and a host of embedded systems other than those that directly control water treatment and supply (for example, internal telecommunications equipment, building HVAC and security systems, automated sampling and analytical equipment).
(See the Association of Metropolitan Water Agencies (AMWA)  website http// The AMWA website also has a full list of equipment, instruments and systems that must be checked for embedded chip problems at water treatment plants..)

Indirectly (external to the water treatment facility), drinking water quantity and quality also depend on:(external to the water treatment facility), drinking water quantity and quality also depend on(external to the water treatment facility), drinking water quantity and quality also depend on

--Electricity generated by fossil fuel (oil, gas and coal) and/or nuclear power plants;

    --Adequate supply and timely delivery of treatment and disinfecting chemicals from chemical manufacturers and suppliers;

      --Telecommunications support from phone companies and equipment manufacturers that permit the operation of supply chains of electricity, treatment chemicals and interactions with customers;

      --Maintaining protection of the sources of water. (For example, the quality of surface water such as streams and rivers could be degraded by Y2K-related failures of upstream municipal and industrial wastewater treatment facilities.)

The most comprehensive source of information about the Y2K readiness of water utilities is a voluntary survey conducted jointly in July/August of 1998 by AMWA, the American Water Works Association (AWWA) and the National Association of Water Companies (NAWC).     Out of 3700 utilities (which together serve a total of 204 million people) that received a survey, 725 responded, a response rate of about 20% .  Statistically, a voluntary survey with a response rate of  20% cannot be used to draw conclusions about the population of 3700 systems.  If the nonresponding utilities are less prepared than those that did respond, then the survey results are misleading.  According to AWWA, however, response rates for the two largest categories of water utilities were 100%. Survey questions related primarily to the status of internal Y2K planning, implementation and testing; external planning, implementation and testing (i.e., Y2K compliance status of external service providers and vendors); and contingency planning status of the water utilities.

 In terms of internal Y2K readiness of the responding utilities, 81% were confident at the time of the survey that they would complete their internal Y2K planning, implementation and testing in time for the year 2000.  The percentages were higher for large and very large systems, 89% and 100%, respectively, than for smaller water systems.

 Utilities were less confident that all their external Y2K planning, implementation and testing would be complete before the year 2000 begins. Thus, only 67% of large and 90% of very large utilities were confident that they would not be affected by "power outages, communications failures including data transmission, or a shortage of water treatment chemicals if their external service providers and vendors have Year 2000 problems". The overall percentage was 65%.

Finally, at the time of the AMWA survey (July/August 1998), only 27% of responding water utilities had Y2K-specific contingency plans. Since last summer, this proportion has probably gone up, however.  Contingency plans would include such things as making sure the utility can operate systems manually, filling water storage tanks to capacity, and stockpiling fuel and treatment chemicals in the event of supply chain disruptions.

 Why Should You Prepare for Potential Water Supply Disruptions? Why Should You Prepare for Potential Water Supply Disruptions?Why Should You Prepare for Potential Water Supply Disruptions?

While the apparent internal readiness of large, and especially, very large utilities is encouraging, the AMWA survey results should not be a reason for complacency.  Given the low response rate of the survey, and the fact that it was a voluntary survey involving self-reported data, it is impossible to assess how biased the survey results are.  The survey also does not give much detail about how far advanced water utilities are in their Y2K remediation plans.  It is clear, however, that even large and very large water utilities were concerned about their external dependencies on suppliers, transportation, electric utilities and telecommunications.  Thirty percent of large and !0% of very large utilities were not confident that this aspect of their Y2K preparations would be complete by January 2000. Furthermore, even if water utilities are internally and externally completely prepared for Y2K, they are still vulnerable to failures of upstream municipal and industrial wastewater treatment facilities. At the time this is being written (2/1999), there is little public information available about the Y2K readiness of wastewater treatment facilities. 

Clean water is cheap in times of plenty, but it can be priceless in times of need. Given the uncertainties in the existing data about water utility Y2K readiness, the complex interdependencies of water utilities with their suppliers and other infrastructure providers, as well as the potentially serious risks of water supply disruptions--water shortages, contamination of water supplies by microorganisms or chemicals (e.g., due to pollution from upstream facilities), waterborne disease outbreaks, etc.-- personal contingency planning for clean drinking water is a common sense precaution for individuals and families to take. Such personal preparedness can be viewed as a form of health insurance.

How Can You Prepare for the Possibility of Water Supply Disruptions?

 Preparing for possible water supply disruptions should involve at least two things: some level of water storage as well as a means of treating water of questionable quality.  In addition, depending on your assessment of the potential severity of water supply problems in your area, a third component might be of interest, namely water collection.   Each of these subjects will be discussed below.

Water Storage

 The most reliable way of insuring a minimum supply of clean water for times of emergency is to store some.  The following recommendations for a water storage program are adapted from the book, Making the Best of Basics: Family Preparedness Handbook:

1. Store water from the source that you are currently drinking from, so that household members do not need to become accustomed to different-tasting water.

2. Water should be stored in new, heavy duty, food-grade plastic containers that have been thoroughly cleaned and have tight-fitting lids.  Food-grade containers are made of materials that meet Food and Drug Administration standards for food storage.  Ideally, your water storage containers should also be sturdy enought to meet Department of Transportation standards for strength and transportability (i.e., shipping grade containers). These come in various sizes from 5 to 55 gallons. Five gallon containers are generally designed for stacking and weigh about 40 pounds filled with water, which is about the maximum that most people can readily carry. Fifty-five gallon food grade plastic barrels with a siphon pump are also available for storing larger quantities of water. Containers should be cleaned thoroughly with anti-bacterial soap and then be permitted to air-dry.

3. Do NOT reuse lightweight plastic containers previously filled with food or, especially, with chemicals.  Remnants of previous contents, even though they may not be readily detectable by smell or color, may result in a contaminated water supply.

4. Store water away from paint, petroleum based products, acids or anything that smells bad such as equipment, animal waste, fertilizer, etc.  Plastic containers "breathe", so they can become contaminated by substances with strong odors, especially petroleum based products.

5. Never use metal containers for water storage.  Some have a coating on the inside that can give stored water an unpleasant taste, and some will rust.

6. Rotate your water supply in order to insure its quality and shelf life. In theory, bacteria- free water that is stored in clean, tightly closed containers away from sunlight will stay safe for several years.  However, unless you plan to sterilize water and containers at the time of storage,

 is always better to rotate stored water supplies every 6 months, if at all possible.  If stored water has not been rotated regularly, then treatment prior to use (with bleach, for example) can be used to insure that water is drinkable (see below).

While Stevens  does not recommend the use of lightweight food containers for water storage, clear plastic drink containers previously used for soft drinks, fruit juices and bottled water (the ones that say #1 and PETE in the recycling symbol on the bottom) can be reused for water storage if they are cleaned thoroughly before use. Since these bottles were not specifically designed for longterm water storage, however,  it is probably prudent not to store them outdoors or at freezing or very high temperatures, particularly once they have been filled with water.  They should also be stored out of the sun.  Note that translucent (#2 HDPE) plastic milk jugs should NOT be used for water storage since they are biodegradable, plus milk residues may contaminate water stored in them.

One of the simplest, cheapest things you can do NOW to start a water storage program is to start cleaning out and saving clear plastic (#1, PETE) soda bottles each time you finish one, instead of recycling them or throwing them away.

For people who wish to store larger quantities of water outdoors, it can be stored in large outdoor tanks or cisterns.   These come in several different materials ( e.g., linear polyethylene) and many different sizes and can be purchased from a number of suppliers, including Coastal Technical Sales, Poly Processing, Tank Town, Jade Mountain and Real Goods (websites and telephone numbers are given in the bibliography). Be sure the  tank you purchase is approved for drinking water storage.  To be used as an emergency water supply, water tanks can be filled with tapwater from an outdoor faucet while water is plentiful, and later used as drinking water with minimal treatment (see "Disinfecting water with bleach" under Water Treatment).  In an emergency, such a cistern could also be refilled with rainwater from gutter downspouts.  However, it should be emphasized that roof runoff is not clean, and must be extensively purified before using it as drinking water, since it can contain microorganisms as well as toxic leachates from roof shingles (see section on "Water Sources" below).

How Much Water to Store?

Perhaps the surest way to have enough drinking water for your family in case of  supply disruptions is to store it.  The following discussion assumes a two week supply of stored water per person.  Two weeks, it should be emphasized, is an arbitrary length of time. It is NOT based on an assessment of the length of possible water supply disruptions due to the Year 2000 problem.   Rather, it is based on the maximum amount of space most people might reasonably devote to water storage, and on the assumption that water supply disruptions (whatever the cause) might involve intermittent shortages or contamination, and that some minimum amounts of clean water would be available, if at higher prices. A two week supply of stored water would also permit a household to help unprepared neighbors in the event of shorter duration water supply problems.

Stevens distinguishes between subsistence and maintenance level water storage requirements.  The minimum approach recommended for insuring that a household has at least a subsistence-level water supply for water emergencies is to store one gallon per day per person for a two week period. Thus, assuming a four- person family, this comes out to:

1 gallon x 14 days x 4 people = 56 gallons.

 The subsistence level provides barely enough water for each family member for drinking, brushing teeth, and washing hands with a washcloth, but it is not enough water for food preparation.   Note that drinking at least 2 quarts/person per day is recommended; and high levels of physical activity, hot weather, illness, and nursing a baby  are all likely to increase water needs over and above two quarts/day.

 A slightly more generous level of water storage than the subsistence level  is two gallons per day per person for a two week period, which is equal to:

2 gallons x 14 days x 4 people = 112 gallons,

or approximately the contents of two 55 gallon drums.  Stevens calls this a maintenance level of water storage. This permits some water use for cooking and food preparation, cleaning utensils and equipment, and for washing the body with a washcloth.  It should be noted that both subsistence and maintenance levels of water storage provide only a fraction of the amount of water most Americans use in a day.

This paper will not discuss what to do about wastewater disposal (flushing the toilet, etc.) in the event of public water supply disruptions.  This subject is covered in NOVA Y2K's waste disposal paper.

Water Sources

In the event of unexpected water supply disruptions, whatever the cause, a number of indoor and outdoor emergency water sources can be utilized (see Appendix 1). Note that water from some of these sources cannot be considered drinkable without prior treatment!  Water treatment will be discussed in the following section.

 If clean interior water sources such as the plumbing system are exhausted, two obvious emergency water sources are rainwater and snow.  However, unless rainwater or snow are captured directly as they fall from the sky in clean containers, they cannot be used without prior treatment.

In some places, for example, Texas,  rainwater harvesting for household use is being practiced by increasing numbers of people, and is actually encouraged by the state government. With an appropriate water collection surface (usually a house roof made of an appropriate material such as metal or slate), a water storage system, and access to a modest source of electricity, a household can satisfy all its water needs through rainwater collection, as long as average annual rainfall exceeds 30 inches per year. The Texas Guide to Rainwater Harvesting and Banks and Heinichen discuss the theory and practice of rainwater collection for household use in some detail, and the former publication also provides a number of Texas case studies. Such relatively elaborate rainwater collection systems may be more than most people are willing or able to install purely as an emergency water source for possible water supply disruptions, however.

 What most people in single family homes or even townhouses  can afford to install is one or two rainbarrels under their gutter downspouts. Rainbarrels can be had through gardening catalogs (e.g., Gardener's Supply Catalog) or local suppliers.  In a pinch, even a brand new garbage can can be used as a rainbarrel.

It is important to emphasize here that while rainwater as it comes out of the sky may be clean (apart from the presence of  airborne pollutants), water that comes off a roof is not clean enough for drinking and cooking! It can contain a whole range of potential contaminants from trees, birds, insects, etc.  Furthermore, many roofs these days are made of composite asphalt shingles or other materials that can leach toxic substances into the rainwater as it runs over the roof surface.  Thus, water that comes off a house roof MUST be treated before use! However, while this water should not be used for drinking water purposes without extensive treatment (e.g., distillation or a series of filters, depending on the contaminants of concern), it may be useable as is in an emergency situation for washing or rinsing things other than food or drink containers, for instance, bathing, washing clothes, flushing the toilet, etc.

Finally, in an emergency situation,  rainwater can be collected directly in clean containers with a large surface area (i.e., without first running off a dirty collection surface such as a roof), in clean backyard kiddie pools, for example, and it will require only minimal or no treatment before use as drinking water, depending on the cleanliness of the container in which it is collected.

Water Treatment 

  Water storage is probably the best way to ensure that you have a source of clean water in the event of any kind of water supply disruptions, including possible Y2K related ones.  However, water is heavy (8 lb/ gallon) and takes up a great deal of space.  Thus, because water is so essential to life, a well-prepared household should also have at least one or more means of treating water to make it drinkable. Having the ability to treat potentially contaminated water also allows people to help neighbors who may not be prepared.

Water contaminants can be one of three general types: particles such as debris and sediment, chemical contaminants, or biological contaminants. Elimination of debris or sediment from water is usually done with some kind of large-pored filter.  Debris can be removed by simply filtering water through several layers of densely woven cloth. For smaller particles, various kinds of sediment filters are available, which will be discussed further below.

Water that is contaminated with microorganisms or toxic chemicals need not look, smell or taste bad! Elimination of biological contaminants from water is referred to as "disinfection" of the water. Chemical contaminants CANNOT be removed by disinfection but can be eliminated by a variety of filters or by distillation. Water can be disinfected through the use of heat (boiling) or light (ultraviolet light), by chemical methods such as chlorine or iodine, or by filtration or distillation of the water. Table 2 summarizes the uses and effectiveness of various water treatment methods. (Table 2 and much of the section on water treatment are based on The Drinking Water Book, by Colin Ingram.)

Simple water disinfection without equipment

The boiling method.One of the simplest ways of treating contaminated water or water of questionable quality in order to make it drinkable in an emergency is to boil it  at a rolling boil for at least 10 minutes.   Note that debris should be filtered or strained out of the water before it is boiled (some light but densely woven cloth will do for this purpose). Obviously,

disinfection of water by boiling requires a heat source and fuel.  Boiled water can be made to taste less "flat" by pouring it back and forth between two containers a number of times (aeration), by letting it stand for a few hours, or by adding a pinch of salt to each quart of water.    Note that while boiling can kill microorganisms present in water and remove some volatile chemicals,  it does not remove nonvolatile chemicals (i.e., most kinds of chemicals) or toxic metals (for example, those that might be present in runoff from roofs with composite shingles).

Water disinfection with chlorine Water can also be disinfected using chlorine in the form of household bleach, granular calcium hypochlorite, or chlorine tablets.

Table 2: Click to view comparison of treatment methods:. Water Treatment

Household bleach such as Clorox, which usually contains 5.25% sodium hypochlorite, can be used to treat reasonably large quantities of water relatively cheaply. The bleach used should be plain bleach with no soap additives, phosphates or perfumes. Stevens gives the following instructions for treating water with bleach:

Disinfecting water with bleach:

1) If water is clear, add 8 drops of bleach per gallon of water, or teaspon per 5 gallons.
     If water is cloudy, add 16 drops bleach per gallon, or 1 teaspoon per 5 gallons.

(Do not add too much bleach.)

2) Thoroughly mix bleach in water by stirring briskly.

3) Let water stand for at least 30 minutes.  The mixture should have a distinct bleach (chlorine) smell or taste after the waiting period. If no chlorine smell is detected, add the same dose of bleach to the water and let mixture stand an additional 15-20 minutes.   Note that the colder and dirtier the water is, the longer is the time needed for the chlorine to kill microorganisms.   If the chlorine taste of the treated water is unpleasant, the water can be poured from one clean container to another several times, or be allowed to stand exposed to air for a few hours.

Disinfection with calcium hypochlorite Another way of treating contaminated water with chlorine is to use high-test granular calcium hypochlorite, which is sold, among other places, in swimming pool supply stores as HTH (for "high-test hypochlorite"). This calcium hypochlorite has between 65-75% of its weight as available chlorine.  One virtue of buying granular hypochlorite rather than Clorox for water disinfection is that more disinfecting power can be stored as a solid in a smaller volume.

In order to use granular calcium hypochlorite for emergency water disinfection, you must first make what is called a "stock solution" by dissolving one heaping teaspoon (about 1/4 ounce) of high-test granular calcium hypochlorite per two gallons of water.  This "stock solution" is NOT drinkable! In order to disinfect questionable water, add one part of your stock solution to each 100 parts of water to be treated.  This is approximately equivalent to adding 1 pint of stock chlorine solution to each 12.5 gallons of water to be disinfected. To remove excessive chlorine odor after disinfection, water can be aerated by pouring from one container to another.

Chlorine tablets Chlorine tablets for disinfection of drinking water can also be purchased from some drug or sporting goods stores and should be used as stated on the package. When no instructions are available, use one tablet to disinfect each quart of water to be treated.

Water disinfection with iodine Iodine tablets for drinking water disinfection can also be purchased at some drug or sporting goods stores, and should be used according to instructions. If no instructions are available, one tablet should be used for each quart of water to be treated.

Tincture of iodine (a 2% solution of iodine) from a first aid kit can also be used to disinfect water. To use for water disinfection, 20 drops of USP tincture of iodine should be added per gallon of clear water; or 40 drops per gallon of cloudy water.

Water disinfection with  iodine has several drawbacks, however.  Some people cannot tolerate the odor or taste of iodine- treated water.  People with thyroid problems should not drink iodine treated water because of possible effects on their thyroid condition, nor should it be used by pregnant or nursing women. Also, iodine may not be effective against organisms such as Giardia or Cryptosporidium, and should thus not be used for disinfecting water from surface water sources (lakes, rivers or springs).

Water filters and other water treatment units

Water that is of questionable quality can also be treated using various kinds of water filters and other treatment/purification devices.  There is currently a bewildering array of such devices on the market in a wide range of prices.  In this section, I will make a brief attempt to demystify this technology.  Most of the following discussion is based on The Drinking Water Book by Ingram.

 The four main types of water treatment or purification units are filters, distillers, reverse osmosis units (which can be viewed as a type of filter), and purifiers that use ultraviolet (UV) light.  Except for some camping and travel type filters,  most of these units are designed for stationary use at one location, that is, they are not readily portable.  Also, distillers and UV purifiers require electricity.

Characteristics of water filters.

Water filters can be divided into several basic types: sediment filters, carbon filters, filters for microorganisms, mineral/metal filters, and reverse osmosis units.  These basic filter types can either be purchased separately, or in some cases, as part of a single unit.  Some water filters are incorporated in portable units intended for water treatment when camping, travelling or for emergency use in a disaster situation, or they can be part of a larger stationary home water purification system.  

Sediment filters are often used as the first stage in a drinking water purification system to keep the following stages from becoming clogged up. They are not designed to be used alone.  They filter out dirt and other particles and are rated according to the smallest particle sizes they can trap.  For example, a 5 micron filter will trap particles that are 5 microns in diameter or larger.  With a dirty water source, two sediment filters may be used in conjunction, a coarser (50-100 microns) filter first, and then a finer (5 micron) one. Pleated-film type sediment filters tend to last longer before they are clogged up and are more resistant to bacterial growth than the wound-string or rigid foam type sediment filters.

Activated carbon filters can be either granular or block carbon filters. They are used to remove a wide variety of chemical pollutants from water, but they CANNOT remove microorganisms or dissolved minerals.  Carbon filters are especially useful for organic chemicals such as pesticides, herbicides and industrial chemicals. They can also remove radon, chlorine, and unpleasant tastes or smells. Carbon block filters are more effective than granular carbon filters, because channels often develop in the granular type where water can flow through without contacting the carbon. However, the dense pores of carbon block filters can easily become clogged unless they are preceded by a sediment filter. Also, as mentioned above, carbon filters cannot disinfect water (that is, they do not remove microorganisms); in fact, they may provide a breeding ground for organisms.   For all these reasons, carbon filters should be replaced at regular intervals. Many of the most commonly sold household water filters are some kind of activated carbon filter. One of their most common uses is for removing chlorine from municipal water supplies.

Filters for microorganisms. Three classes of waterborne microorganisms that need to be eliminated from water in order to make it drinkable include bacteria, parasites and viruses. Filters used to remove parasites and bacteria from water include ceramic and membrane (reverse osmosis) filters.  Ceramic filters with a pore size of about 0.2 microns are used extensively by disaster relief agencies such as the International Red Cross and by armies of many countries.  These ceramic filters are sturdy (as long as they are not dropped on a hard surface) and portable, and can be used indefinitely since they can be cleaned by scrubbing them periodically. Viruses, because they are so small (<0.1 micron), cannot be removed with most filters, with two exceptions discussed below.   

Two filters that are at least partially effective in removing or inactivating viruses in water are ceramic/silver filters, and iodine-resin filters.  The iodine-resin filter uses a microfilter to trap cysts and parasites, and iodine that is tightly bonded to a resin filter medium kills waterborne bacteria and viruses.   According to Ingram, iodine resin filters are thought to be more effective against viruses than ceramic-silver filters. However, ceramic-silver filters can be used indefinitely, while iodine-resin filters must be replaced periodically.

Membrane filters are used in reverse osmosis (RO) water purifiers.   Reverse osmosis purifies water by letting it pass through a thin membrane with very tiny pores or holes. Larger pollutant molecules are left behind because they cannot get through the pores.   The advantage of  RO is that it removes a wide variety of pollutants from toxic minerals and organic pollutants to some microorganisms. However, because the pores of the reverse osmosis membrane are not uniform in size, this method can only partially remove microorganisms from water, and should not, by itself, be used for disinfection of water.  Some other disadvantages of reverse osmosis units includes the fact that they tend to waste water and that the filtering process is very slow. Also, use of RO in a low pressure water system may require use of a booster pump to force the water through the RO membrane. Finally, the RO membrane is rather delicate and can fail prematurely after a few months if there are bacteria or high levels of dissolved solids in the water to be treated.

One other type of filter that should be mentioned here is the mineral/metal filter.  These include two kinds: alumina and redox filters.  They can remove dissolved metals such as lead (as opposed to metals that are in the form of particles).  Alumina filters attract and trap dissolved metals, but do not remove chlorine, organic chemicals or microorganisms. Redox filters (short for reduction/oxidation) exchange toxic metals in water for zinc and copper. Redox filters can also partially reduce levels of bacteria in water and trap chlorine. The performance of an alumina filter deteriorates with time faster than that of a redox filter.

Home water purification systems

The filters discussed above include both portable and stationary types.  Some, such as ceramic-silver and iodine resin filters, can be made eminently portable and are often used for camping, travel or emergency use. Some, e.g., sediment filters,  are used almost exclusively in combination with other types of filters or water treatment devices.  Home water purification systems often involve a combination of two or more types of filters or other water purification devices. They range from water pitcher, countertop and undersink styles to whole house systems.  Ingram reviews and analyzes the effectiveness and costs of some of the best home water purification systems. These range from various kind of filters to reverse osmosis, distillation, and ultraviolet type purifiers.  Ingram explains which combinations of treatment approaches are most effective against which kinds of water contaminants, including microorganisms, minerals, organic chemicals, radon, additives such as chlorine, and undesired tastes and smells, and he discusses the pros and cons of specific models and combinations of units.

Two remaining types of water purification devices, distillers and ultraviolet (UV) type water purifiers, that are used in home treatment systems have yet to be discussed.  Both require electricity, so use in a power outage is not possible unless you have an alternate power source. Distillers work by turning water into steam and then recondensing it, so that impurities that do not evaporate are  left behind.  The virtue of distillers is that they can produce high quality water very reliably, and they can remove all types of pollutants except some volatile organic chemicals (which evaporate when the water evaporates). A disadvantage of distillers is that they require a good deal of electric power to heat and evaporate the water. Also, water cooled distillers waste water (4-5 gallons per gallon of purified water made). Air cooled distillers waste less water but are not as energy-efficient as water cooled distillers.

Ultraviolet purifiers disinfect water using a special ultraviolet lamp. Thus, they require electricity, but not as much as distillers.  UV purifiers only disinfect water, and they cannot remove chemicals from water. Thus, UV purifiers must be used in combination with filters if chemical water contaminants are a concern. Also, UV purifiers require sediment prefilters, since solids or particles in water can shield microorganisms from the UV light.  If  cysts such as those of Giardia are a concern (which have hard coverings that UV light cannot penetrate), a carbon block filter must also be used, and if toxic minerals are present, a redox filter must be used as well.

What are the best water treatment methods to have in case of possible Y2K disruptions?

 Unless you can be certain your water utility will have no problems whatsoever due to the Y2K problem, it is prudent to combine some level of water storage, as discussed above, with one or more water treatment options. The level of precautions any particular individual or family takes is likely to depend on a number of factors, including state of health of family members, knowledge or assumptions about theY2K status of local infrastructure, financial circumstances, degree of risk aversion, and other considerations, e.g.,  environmental concerns.

The cheapest and easiest means of disinfecting water (i.e., killing microorganisms in water) is to buy a couple of extra bottles of Clorox at the grocery store.  At  8-16 drops per gallon of water to be disinfected, a gallon bottle of Clorox will disinfect over 7000 gallons of clear water (and half that much cloudy water).  As discussed in the NOVA Y2K  waste disposal paper, Clorox can also be used to disinfect human wastes when flushing toilets is impossible.  Other relatively inexpensive chemical disinfection options are calcium hypochlorite or some form of iodine.  It should be noted, however, that at least two organisms, Giardia and cryptosporidium, may not be entirely eliminated by chlorine or iodine treatment, and iodine should not be used by some people. If a heat source and fuel are available, then boiling water at a rolling boil for 10 minutes is an excellent means of disinfection that can also kill Giardia and cryptosporidium.

Portable water filters sold for camping, travel and disaster preparedness provide another relatively inexpensive means of disinfecting water (many cost less than $150). Filters have the virtue of not requiring a heat source like boiling water does; they do not introduce chemicals into the water; and they can be taken along whereever you go. Also, ceramic filters also have a very long working life.

 Various portable filters are sold by suppliers such as Real Goods, Jade Mountain, camping outfitters such as REI and LL Bean, emergency preparedness suppliers such as Emergency Essentials and Majors Surplus and Survival, and others.  Some of the most highly regarded portable filters are made by Katadyn, PUR, and First Need. The Katadyn Pocket Filter can eliminate bacteria and parasites from untreated water and  is used by the International Red Cross and armed forces of many countries.  It is a very fine (0.2 micron) ceramic filter that can last through many years of use.   The Katadyn Combi combines a ceramic filter and an activated carbon filter so it can remove both microorganisms and many chemicals from water; but the carbon filter element has a limited life span.   PUR also makes a variety of filters such as the PUR Explorer which combine a microfilter and an iodinated resin to eliminate viruses, bacteria and Giardia. However, the filter cartridge must be replaced periodically (the PUR Explorer cartridge lasts for up to 100 gallons.) 

Another popular portable water filter that is recommended in The Solar Living Sourcebook is the First Need filter, which has the same proprietary filter matrix as the Seagull brand filters.  According to the Solar Living Sourcebook, these filters will remove giardia, cysts, bacteria, larger parasites, chlorine, lead, and many organic chemicals, among other things.  Thus, the First Need filter combines qualities of an activated carbon and a bacterial filter. The First Need filter cartridge must be replaced after about 100 gallons, and can also be outfitted with a replaceable sediment prefilter.

In addition to the highly portable types of filters sold for camping, travel and emergency preparedness purposes, there are also home water purification units, including reverse osmosis units and distillers, that come in relatively portable countertop models which are less expensive than undersink type units (i.e., $400 or less in 1995).  Ingram describes some of these units, for example, the Waterwise and Ecowater distillers.  As mentioned above, one potential drawback of distillers is that they require a fair amount of electricity.   Manufacturers of countertop reverse osmosis units mentioned in The Drinking Water Book include Challenger Water International, Water Factory Systems, Water Products International, and DeltaAqua, Inc.   Reverse osmosis units generally require water pressure of at least 35 pounds per square inch, i.e., they are not drip filters. Katadyn sells a countertop type ceramic drip filter that is more more convenient for home use than its Pocket Filter; however, like other ceramic filters, this unit does not address chemical pollutants.  Finally, Seagull filters, which have the same proprietary filter medium as the First Need, mentioned above, come in a countertop model with a hand pump so it can be used with nonpressurized water systems.

Testing Water Quality

Discussion of water quality testing is beyond the scope of this paper. However, Ingram has a good discussion of water testing in The Drinking Water Book..  He points out that water quality testing can be exceedingly expensive, but that some reputable test labs offer comprehensive automated testing for reasonable prices (which can still run several hundred dollars for a complete battery of tests).  Two labs that Ingram mentions are Spectrum Labs and National Testing Laboratories.  It is also possible to get a list of certified water testing labs from EPA's Safe Drinking Water website or hotline.


Based on studies of hurricane and earthquake preparedness, some proportion of people in a community will not undertake any kind of personal contingency planning for Y2K, either because they are unwilling or unable to do so. In order to help those who cannot or will not prepare themselves, local governments can undertake some relatively simple and inexpensive actions before the end of 1999 to help insure some protection from water supply interruptions or contamination for all its citizens.  These might include such things as filling public swimming pools with water, purchasing some large water tanks and a store of disinfectants such as calcium hypochlorite, and requiring citizens to save containers that can be used for water storage which would otherwise be recycled (such as PETE soda bottles). 

A community water utility that is well prepared for possible Y2K problems will have developed a variety of contingency plans for different internal and external failure scenarios.  However, few communities have the ability to store large amounts of  finished drinking water.  Most large drinking water systems have 2-5 days storage capacity. Because clean water is so critical to human health, personal preparedness for possible water supply disruptions is an important form of insurance.  Being prepared also makes you part of the solution, rather than part of the problem. Every person who is prepared is one fewer individual that is dependent on emergency response organizations, if water supplies are disrupted by Y2K problems or any other emergency.  

Sources of Information & Products

Real Goods Company: 1 (800) 762-7325, Real Goods Renewables: 1 (800) 919-2400,
Jade Mountain: 1 (800) 442-1972,
Harmony: 1 (800) 869-3446,
Emergency Essentials: 1 (800) 999-1863 ,
Major Surplus & Survival: 1 (800) 441-8855
REI (Recreational Equipment Co.) 1 (800) 426-4840,
LL Bean: 1 (800) 221-4221,
Gardeners Supply Company: 1 (800) 863-1700,


 Above-ground outdoor water storage tanks can only be used in colder regions of the country in winter if they are insulated, for example with fiberglass or polyurethane; otherwise they can crack if the water inside freezes.

Note that rainwater collection has important environmental benefits, since it can help people conserve water and helps retard stormwater runoff (which can cause downstream flooding and damage to streams and rivers.) While people in the eastern U.S. often think of water scarcity as a Southwestern problem, high population growth in metropolitan areas like Washington, DC, is causing planners to start thinking about means of reducing water demand (Drinking Water Supply in the Washington, DC Metropolitan Area: Prospects and Options for the 21st Century, League of Women Voters, February 1999).

 It is important to distinguish between water treatment that makes water quality acceptable for short-term use in an emergency, and water purification that makes water suitable for long-term use.

Removal of debris and use of a sediment prefilter is desirable with all water treatment methods. It is particularly essential for a carbon block filter, reverse osmosis, and UV disinfection.  Carbon block filters and reverse osmosis membranes are easily clogged, and water turbidity (cloudiness) reduces the effectiveness of UV disinfection.

Carbon block filters (even though their rated pore size is smaller than most bacteria) cannot be used to remove bacteria and parasites from water because the carbon pore size is not uniform enough and the seals around the filters permit some leakage.

 According to Katadyn Products, Inc., ceramic filters have some ability to remove viruses because many viruses in water are attached to bacteria, so that by filtering out bacteria, viruses are partially removed also.

 Telephone numbers and websites of suppliers are given in the bibliography.

  At the time this is being written (1/1999), Katadyn ceramic filters are already on backorder at a number of distributors due to unusually heavy demand, presumably due to Y2K concerns.

Copyright © Ingrid Shulze


Copyright ©  Sally Strackbein
Permission is granted to reprint a few
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in your magazine, website or newsletter
with the byline:

"Sally Strackbein is a speaker and author.
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