Water Clarification And Purification


To get safe drinking water may require a process of clarification and then purification.

Here are the details including water filtration and various methods to purify water…



Water foraged from natural sources is often contaminated with dirt, debris and suspended particles. Water should be clarified before placing it into the water filter or purifying it by other methods.



Settling is the easiest method for clarifying and removing debris and suspended particles from the water. If the water is muddy or murky, settling it before filtering will extend the life of the filter. To let water settle merely let it stand in a large container, totally undisturbed for 12 to 24 hours. This will allow any sediment (including radioactive particles) to sink to the bottom. A handful of clay soil in each gallon of water will help speed this process. After settling is complete, pour, dip or siphon the clean water into another container, being careful not to stir up the sludge at the bottom.

Can Filters:

Clean a large can (#10 or a large juice can, etc.), and using a nail, punch several holes in the bottom of the can near the center (avoid making holes near the edges of the can). Place an inch or two of washed, crushed charcoal in the bottom of the can (purchased at any pet shop or taken from a fire). Cover the charcoal with 3 or 4 inches of glass wool or polyester aquarium filter. In an emergency, paper towels, toilet tissue, pieces of cloth or even dried grass will suffice. Be sure to pack the material tightly against the sides of the can so that no water can leak around it without being filtered. Suspend the can above a clean container. Pour the polluted water into the can, and allow it to drip into the clean container below. This type of filter will clarify up to 2 gallons of water per hour.

Earthen Filters:

Effective for radioactive water. Clay binds to radioactive particles. If radioactive fallout has contaminated the water supplies, earth filters utilizing clay type soil, will effectively remove the radioactive particles from the water. This method is better than distillation, ion-exchange filters, or charcoal filters for this purpose. Perforate the bottom of a 5-gallon can or wastebasket with holes punched within 2 inches of the center. Place a two-inch layer of washed pebbles on the bottom of the can. Cover the pebbles with one thickness of terry cloth towel or other porous cloth. Scrape the top 4-5 inches of soil off the ground to get below the fallout, and dig enough clay-type soil to fill the can to a depth of 8 inches, packing it tightly against the sides. Cover the soil in the can with another thickness of toweling and another one or two inches of pebbles. Suspend the can over a clean container and pour the contaminated water into the top. Clear (but unpurified) water will come out the bottom at the rate of about 6 quarts per hour.

Hose Siphoning:

Take a six to eight foot section of garden hose and push two cotton balls into the end. Place that end of the hose into a bucket or container of muddy water. Suck on the other end until water begins to come through. Place the free end of the hose into another container placed below the muddy container. Gravity will pull the water from the higher container into the lower container while trapping the sediment in the cotton balls and allowing only clear water to flow through the hose. When the cotton balls become clogged, simply remove them and replace with clean ones. This filter will clean approximately one quart of water in thirty minutes. However, if the water is very muddy, the cotton balls will have to be replaced very frequently.

Capillary Siphoning:

This filtration method will eliminate most particles and silt from the water. Elevate a container of polluted water above another container and run a piece of braided yarn, strips of cloth (cotton works best), or terry-cloth towel between the two containers as a filtering medium. It helps to soak the material in clean water first, to get the process started. Dirt and debris will not be pulled into the filter, but will remain in the top container. Clean water will pass through the medium and drip into the container below. Capillary action filters are quite effective, but are very slow, clarifying only about one cup of water per hour.

Coffee Filters:

Coffee filters are an excellent filtering medium. Place three or four of them (one inside the other) into a mason jar and let the edges protrude over the rim of the jar. Screw on a jar ring to hold them in place and pour the muddy water into the filters. The water will pass through the filters and drip into the jar. When the filters become clogged, simply replace them. This type of filter will clarify approximately one quart of very muddy water in two hours.




After the water has been clarified, it is ready for step #2, purification. Water should not be consumed until it has been purified.



Water sterilization by boiling is preferred over ANY method of chemical disinfection, because disease-causing microorganisms cannot survive the heat from a sterilizing boil. If the water is cloudy, heat sterilization is the only method that can be fully relied upon to assure complete destruction of these organisms. These organisms can “hide” by burrowing into the microscopic particles that cause cloudiness in water, thereby escaping the action of disinfecting chemicals, and remaining capable of producing disease. Water that is boiled vigorously for five minutes will usually be safe from harmful bacterial contamination. One additional minute should be added for each 1,000 feet of altitude. The use of a pressure cooker (bring the water up to 15 pounds and then remove from the source of heat), conserves the most amount of fuel, if that is a concern. This guarantees that all bacteria, protozoa, and viruses have been killed. To improve the taste of boiled water, add a little charcoal from the fire to absorb odors. Pour it back and forth between two clean containers to mix the water with air.

Chemical Sterilization:

Regardless of the method of chemically disinfecting water, always double the dosage amount if the water is not absolutely clear. If the water temperature is cold (below 45 degrees), wait one hour to allow the disinfectant to work before drinking the water.

Iodine Tablets:

Iodine tablets in the form of tetraglycine hyperiodide are very effective against all forms of bacteria. This form of iodine, however, is less effective against the dreaded protozoa, GIARDIA LAMBLIA. Iodine tablets are sold in sporting-goods stores under the names of Coghlan’s Globaline, and Portable Aqua. Iodine tablets usually have a relatively short shelf life (losing 20% of their effectiveness in just six months). They are also very sensitive to heat and light. They turn color from grey to yellow as they become less potent. The usual dose is one tablet per quart of clear water, and two tablets for cloudy water. Let the water stand for 30 minutes before using.

Tincture of Iodine:

A 2% solution of tincture of iodine, as found in most first-aid kits, can be added to polluted water. Use 32 drops of tincture of iodine per gallon of clear water, or 8 drops for a quart, and let it stand for 30 minutes before using. Double this amount if the water is cloudy.


Hypochlorite must be the ONLY active ingredient in liquid household chlorine bleach intended for use in purifying water. Do not use granular or powdered forms of household bleach, as they are poisonous!! Add 2 drops of liquid bleach per quart of clear water, 8 drops per gallon, or one-half teaspoon for five gallons (approximate). Double this amount if the water is cloudy. Liquid bleach loses strength over time, and in just one year of storage the dosage must be doubled to be effective. Two year-old bleach must not be used. It is not potent enough to kill disease-causing bacteria. After adding the proper amount of bleach to the water, stir and let stand for 30 minutes before drinking. Liquid bleach will kill most common forms of bacteria, but it is totally ineffective against GIARDIA and other hardy forms of protozoa.

Halazone Tablets:

Halazone tablets, the least effective method of chemically disinfecting polluted water, are available at most drug and sporting goods stores. If used, add four tablets per quart of clear water, and eight tablets per quart of water clarified from muddy water. Allow the tablets to dissolve, then shake the water and let it stand for 30 minutes before drinking. The shelf life for unopened Halazone tablets is only 5 to 6 months. If they are left in an opened package,
they can lose their effectiveness within only 48 hours.

Some information sourced from The American Civil Defense Association.


  1. Coffee filters are also great as a pre-filter for your portable, backpacking style water filter to extend the filter life.

  2. This is one thing I’ve always been afraid of. I haven’t worked up the courage to drink actual rain water yet, but I know I have to do it now while I have all the luxuries to make it easy. There’s a canal within like a mile of my house, but people in my town don’t even fish in there. I’d look pretty suspect messing around there to fill a jug right now. I’m quite sure someone would call the police. Rainwater is my best method of practice, at least right now.

    1. Harvesting rain water is an excellent method of water procurement. There are many ways to do this ranging from roof/gutter collection systems to a simple tarp. Filtering and purifying is still advised…

      1. Oh gosh, are you kidding me? Before I drink rain water, I’m going to run it through a coffee filter and boil it for like 10 minutes. I’ll start with drinking one cup and see if I survive. Then maybe I can move up.

        1. When I was a kid, we had a rainwater harvesting system. Being semi-educated hillbillies, we thought it was a cistern. We never did anything at all to the water.

        2. Most of the virgin islands and Bahamas have no fresh water sources and rely 100% on cisterns(rainwater) for all fresh water needs. The water is collected from the roof and dumped into large tanks. They have it so that they can divert the first runoff away from the tanks till the dirt and bugs and bird poo is washed away then it switch’s to fill the cistern.In most areas except high industry areas, rainwater is very clean and needs no filtering. Actually a lot cleaner than most municipal supplies are.

    2. You need to try get over your squeamishness if you are to do well in a survival situation Sonja,Even in the ultra clean pretty packaged world of today,we have some stuff in our water and food you would not chose to be eating or drinking… but we accept as normal and safe.

      They must add chemicals to municipal water supplies to make them safe to drink(I did not say 100% pure and clean just safe)And you still hear of boil water warnings in many localities. If I did not have well water I would feel much safer drinking rain water from my roof than some of the questionable local municipal water supplies with the added fluoride and chlorine and other chemicals they add.

      I take it you eat pasta and cereal?

      No such thing as 100% clean grain.Just take a look at an analysis of processed cereal grain,and see all the extras included along with it. You will never look at pasta or corn flakes in the same way again,but we still need to eat and drink.

      I love both by the way.

      There is a big difference between 100% safe and 100% pure and clean.(mostly price). You can buy grain straight from a farmer’s field for just a few dollars a bushel with all the sticks and pieces of chaff and little bugs and anything else that was collected during harvest and it’s 100% safe to eat as is.But we dont find it acceptable to have whole bugs or leaves in our box of oatmeal or bag of popcorn or navy beans SOOOO…

      After it gets triple cleaned and washed and bagged into a nice package and “inspected” that same grain will cost at least 2 to 2.5 times more than it cost straight from the field.And there is still “some” acceptable amount of dirt and insect parts in it.(just maybe a bit fewer). Is it any safer to eat? I would say no, just less buggy and dirty but no safer.I am sure you could hire sorters to inspect each and every rice grain and corn kernel as it comes out of the bin to exclude every minute piece of foreign matter but you would be paying $100.00 a pound for flour and $50.00 for a box of corn flakes at that rate.

      One of my favorite lines from Seinfeld was when Jerry asked what someone thought the worst part of being blind would be? And he thought it would be that you could never tell if their were bugs in your food and you would always be feeling around with your tongue and it would be awful.

      I am in the camp that life is too short to worry about if i am drinking a bit of dirt or eating a piece of grasshopper leg, day to day, and In a emergency situation you should just be glad you had something to eat and drink at all.

  3. Good information. I was unaware of the earthen filter for radioactive water. Any idea on how much this type of filter will process before the filter becomes ineffective?

    1. That is an excellent question. I cannot say with certainty. I have read about this type of filtration for radioactive particles in water, but I have no conclusive evidence as to how long, etc. I’m sure that there are dependencies such as the type of clay/dirt, its compactness and depth, the extent of the radioactivity, etc. Fortunately, we have not had to encounter this in real life… yet…

      I personally wouldn’t do more than a few gallons at a time before changing it out, especially since it’s just ‘dirt’ for the most part.

    2. Ignoring material which will clog the filter, your major concern will be the concentration of radioactive material. At some point, the filter will become so contaminated that it will have to be replaced.

      A radiation detector is the best way to monitor radiation levels. If you don’t have one, get one from ebay. They run about 40 dollars for a civil defense surplus in like new condition. Get one that indicates the presence of gamma radiation. Alpha and beta radiation is dangerous if ingested but you are trying to avoid that.

      Disposal of the filter should be thought out now. You don’t want to just dump it on the ground or bury it. You run the risk of the concentrated radioactive material being spread and entering your food chain. Think long term storage since some of this stuff will have a half life of 5000 years or more.

    1. Calcium Hypochlorite (Pool Shock) is far better in that it will store well for a very long time, whereas bleach will be degraded after 6 months to a year. If you choose to go the route of Calcium Hypochlorite, be very sure of your research as to the proper mixture.

      The following formula was found on readynutrition.com

      How to Disinfect Water Using Calcium Hypochlorite

      Using granular calcium hypochlorite to disinfect water is a two step process.

      To make a stock of chlorine solution (do not drink this!) dissolve 1 heaping teaspoon (about one-quarter of an ounce) of high-test (78%) granular calcium hypochlorite for each two gallons (eight liters) of water.

      To disinfect water add one part of the chlorine solution to 100 parts water to be treated.

      Let the mixture sit for at least one-half hour before drinking.

      Disclaimer: Do your research and come to your own conclusion before using Calcium Hypochlorite.

      1. Ken, I have been shopping/looking for “Pool Shock” for several years and have never found a product that only contains Calcium Hypochlorite. There are always additional chemicals (inert ingredients). Everyone touts “Pool Shock” but I’ve yet to find one brand that is purely Calcium Hypochlorite without additional chemical compounds.

        Do you have a source or a brand name so that I can switch over from liquid bleach? We have a rainwater catchment system we installed 3 years ago and a total of 1,500 gallons in that system (one is an 1,100 tank). We have the means to collect and store the rainwater but in the event that we need a large quantity of a water treatment chemical (for potable water), we would quickly exhaust our stored supply of liquid bleach.

        1. @Lynn, The inert ingredients with Calcium Hypochlorite are just that – inert. They are apparently added to prevent clumping and are apparently not harmful nor reactive. When purchasing Calcium Hypochlorite, be sure that you choose one with no additional ingredients (other than the ‘inert’ ingredients), such as this one.

        2. Ken, thanks so much. I didn’t realize that inert ingredients would be harmless. And thank you for naming and linking a brand. I had actually looked at that one (and a few others) at Amazon recently. I will go ahead an make a purchase this week. This has been a worrisome item for us for way too long!

  4. just a note of caution on using pool chemicals

    many of them contain additional substances that may be harmful


  5. I have many colanders/strainers used in the kitchen.
    Large debris will be contained using these first and then the holes in the #10 can, then the coffee filter, then the Berkey filter.
    But, I have (20) 30 gallon drums filled and plan on using those to catch rain water.
    And if Berkey fails(I do have extra filters and an extra spigot) then I have pool shock–4 bags will filter 40,000 gallons of water.

  6. Pool Shock:
    1 to 2, then 2 to 1.
    Learn that or write it.
    1 teaspoon of CH to a 2 liter of clean water makes the SOLUTION.
    then, 2 teaspoons of SOLUTION to 1 gallon of dirt water.

    1 to 2, then 2 to 1!!!

  7. Avoid bleach, iodine, halazone, etc like the plague.

    Hydrogen Peroxide is the best and cheapest way to kill the pathogens. Who
    would drink bleach, which reverts to lye, or iodine which upsets the

    1 Tbsp per gallon of clean water will keep it safe for some time. If it’s
    really nasty add more peroxide, it’s killing the nasties with oxygen,
    not you in the process.

    1. All of the municipalities across America and other developed countries use a form of chlorine (bleach) to kill the nasties in our water systems. Without it,it would be impossible to serve the publice with purified drinking water. I agree with your general opinion that if we can avoid it in some way, it would be better. One way or another we need to be sure our drinking water is safe.

  8. Kinda surprised you didn’t mention things like a Berkey. A tee shirt or bed sheet can be used to clarify the water.

    1. @WMW, I try not to post articles that are too long (which is what this one would have been if I listed every method of water filtration I could think of ;) ). To address your comment (and thanks for adding your thoughts), I’ve mentioned the Berkey water filter a number of times throughout this blog over the years (a very good means of filtration – I have two of them) while this particular article just touches on a few methods a little outside the normal. You’re absolutely correct about a piece of cloth (t-shirt) being perfectly acceptable for filtering out sediment.

  9. Truly amazing that this same topic is repeated over and over hundreds of times on prepping websites and they almost all fail to discuss one of the best, cheapist and easiest means of purifying clarified water: UV.
    Save all the clear PET plastic water and pop bottles you can, refill with clear water (clarify and use charcoal filtration for chemical contaminants first), cap and lay it in the direct sun for 6-8 hours, 2-3 days if cloudy. Lay on white or reflective metal roofing if you can. Done. Google SODIS water treatment if you want more info.
    There are also various UV systems ranging from a small flashlight sized battery device to constant flow systems that run on 12 vdc and can treat 3 gal/minute all day long for $200.
    Other methods are good for quick treatment or in very cold weather but filter/charcoal/uv is my go to process.

  10. Please re-think using ashes from fire as ‘charcoal’!
    It is not food grade and is what granny used to make lye for soap!
    And about Chlorine to Jim above – 8 drops to a gallon. Another 8 drops if still cloudy. let it sit out with a cloth over it for a day or two and bye bye chlorine.

  11. best water purifier i’ve tried and i’m sticking to is berkey water filter. Instantly purifies water from any source including stagnant water.

    1. i agree..but it is better if you invest on a good home water purification system. it will benefit your family’s health and safety. reverse osmosis is the ideal one as it can remove contaminants such as arsenic, nitrates, sodium, copper and lead, some organic chemicals, and the municipal additive fluoride.

  12. I have a colony of feral cats that frequent my yard. I have a plastic tub of
    standing water that they drink from. How can I make it safe for them to
    drink. Thanks for the help.

  13. in my bore well water the e-coli is 450 per 100 ml. 30 mg of 30% bleaching powder per liter added reduces the e-coli to under 1 which is the standard.
    can i sell this water commercially at COST for social work in villages in india where there is a water shortage

  14. Hi there . Would the Betkey filter water after a nuclear issue (radiation) etc ? Thank you !!!

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