Water Filter Basics

Written by The Ready Store

One of the most important items that you can have in your emergency supplies is a water filter. There are a variety of ways to clean water and make it safe to drink: boiling, distillation, reverse osmosis, deionization, chemical purification and filtration. In this post, I want to explain the basics of micro porous filtration or more simply said “how a water filter works”. At the end of the post, I have included some excellent reference articles from Wikipedia that include more detailed information on the topic for those that are interested.

Many people use water filters in their homes. They are attached to their faucets or sometimes are used with a water pitcher. Typically, these water filters use some sort of activated carbon filter, micro porous filtration or a combination of the two to purify the water. Portable water filters use the same methods to clean water. Portable water filters are used by hikers, the military, survivalists and other people that are in harsh environments. They allow you to clean suspect water and make it safe to drink.

Here is how a portable water filter works. Most portable water filters use a ceramic cartridge inside to clean the water. At one end of the filter, dirty water is brought in through a pumping action. The pump then forces the water through the ceramic cartridge. The ceramic cartridge is designed to filter contaminants that are 0.2 micrometers or larger. Basically, the filter will allow through water molecules and not much else. Major pathogens and contaminants such as Giardia lamblia, Cryptosporodium and other bacteria will be filtered out of the water. Giardia is commonly found in most back country water sources such as lakes, rivers and streams. Once the water is forced through this ceramic cartridge, it comes out the clean end of the water filter, purified and ready to drink. Pretty simple process. Most portable water filters will pump about a liter of water per minute, depending on the clarity of the water.

The advantages of a portable ceramic water filter:

  • Allows for quick access to safe, purified drinking water wherever you find a water source.
  • Removes debris from the water is it is filtered.
  • Portable and simple to use and maintain.

What a portable ceramic water filter can’t do:

  • Remove viruses from water sources such as hepatitis A and rotavirus.
  • Remove chemicals all chemicals from the water.
  • Remove salt from the water.

Portable water filters like the MSR Miniworks or the Katadyn Combi are great portable water filters and highly recommended. Keep in mind, that ceramic water filters, while designed for outdoor backpacking, hiking and military use, still need to be handled carefully. If dropped or damaged, the filter can get very small hairline cracks in it that will allow larger molecules to get through the filter and make it not safe to use.

http://en.wikipedia.org/wiki/Water_filter

http://en.wikipedia.org/wiki/Microfiltration

http://en.wikipedia.org/wiki/Purified_water

http://en.wikipedia.org/wiki/Ceramic_water_filter

Updated March 31, 2009

12 Comments

  1. John wrote:

    Since potable water is so important for survival in long-term emergency situations, and since filter devices can break and wear out, it is a good idea to buy the maintenance kit and at least one extra set of replacement filters for the filter system you intend to use.

    As you indicated, mechanical filters (the simplest and most cost-effective solution) won’t remove viruses. So you probably need to keep some of the water purification chemical products on hand, too. You use the chemical on the raw water, then use the filter — if your filter has an activated charcoal filter, it will remove some of the unpalatable taste that chemical purifiers leave in the water. To make water that has been chemically treated taste better, you might keep on hand some powdered sports drink (e.g., GatorAde (r)) and dissolve enough in each container of water to mask the taste. The sports drink powder is also useful when you have an illness that causes dehydration — the electrolytes in the drink make it more effective than plain water in staying hydrated.

    April 2nd, 2009 at 1:21 pm
  2. TheReadyExpert wrote:

    Great info. Having a maintenance kit for your water filter is a great idea. We also offer a replacement for the ceramic cartridge and if you can afford to, it is a good idea to keep one of those on hand as well. Each ceramic filter, will purify about 500 gallons of water depending on water clarity. Thank you!

    April 2nd, 2009 at 1:42 pm
  3. Joe Kruger wrote:

    Great article. As you mention, one of the downside of a mechanical filter is that it won’t remove viruses. I’ve heard of filters that incorporate UV light to kill viruses, but I can find very little information about it.

    June 21st, 2010 at 7:31 am
  4. guillermo wrote:

    There is no one who became rich because he broke a holiday no one became fat because he broke a fast. Ethiopia

    August 24th, 2012 at 9:04 am
  5. Marco Johnson wrote:

    As a Newbie, I am always browsing online for articles that can benefit me.

    October 7th, 2012 at 4:36 pm
  6. spoon wrote:

    8 drops of bleach per gallon of water also kills the bugs. Leave sit to evaporate the bleach for 30 minutes.

    September 15th, 2014 at 6:21 am
  7. spoon wrote:

    These guys add a little more. Washington State Health Dept.

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    Purifying Water During an Emergency

    The treatments described below work only to remove bacteria or viruses from water. If you suspect the water is unsafe because of chemicals, oils, poisonous substances, sewage or other contaminants, do not drink the water. Don’t drink water that is dark colored, has an odor or contains solid materials.
    Storing water safely

    The best source of drinking water during an emergency is water you have stored with your emergency supplies.

    Store one gallon of water per person per day–enough for at least three days.
    Store-bought, factory-sealed bottled water is best. Check for an expiration date and replace as needed.
    If you choose to fill your own water containers:
    Collect the water from a safe supply.
    Store water in thoroughly washed plastic containers such as soft drink bottles. You can also purchase food-grade plastic buckets or drums.
    Seal water containers tightly, label with date, and store in a cool, dark place.
    Replace water every six months.
    Never reuse a container that held toxic substances such as pesticides, chemicals or oil.

    Purifying by boiling

    If your tap water is unsafe, boiling is the best method to kill disease-causing organisms.

    If tap water is unavailable, the following may be considered as potential water sources. Water taken from these sources should be boiled before drinking.

    Rainwater
    Lakes
    Rivers and streams
    Natural springs
    Ponds

    Caution: Many chemical pollutants will not be removed by boiling.

    Cloudy water should be filtered before boiling. Filter cloudy water using coffee filters, paper towels, cheesecloth or a cotton plug in a funnel.

    Bring the water to a rolling boil for at least one full minute.
    Let the water cool before drinking.
    Add two drops of household bleach per gallon to maintain water quality while in storage.

    Purifying by adding liquid chlorine bleach

    Treat water by adding liquid household bleach, such as Clorox or Purex.
    Household bleach is typically between 5.25 percent and 8.25 percent chlorine. Read the label.
    Avoid using bleaches that contain perfumes, dyes and other additives. Be sure to read the label.
    Cloudy water should be filtered before adding bleach.
    Place the water in a clean container. Add the amount of bleach according to the table below.
    Mix thoroughly and let stand for at least 60 minutes before drinking.

    Treating water with household bleach containing 5.25-8.25 percent chlorine
    Volume of Water to be Treated Bleach Solution to Add
    1 quart/1 liter 5 drops
    1/2 gallon/2 quarts/2 liters 10 drops
    1 gallon 1/4 teaspoon
    5 gallons 1 teaspoon
    10 gallons 2 teaspoons

    Caution: Bleach will not kill some disease-causing organisms commonly found in surface water. Bleach will not remove chemical pollutants.

    DOH Pub 821-031
    Revised – July 2013

    September 15th, 2014 at 6:26 am
  8. wilson wrote:

    carbon block filters can remove many of the things ceramic filters can’t. check Multipure Brand.

    September 15th, 2014 at 7:35 am
  9. Sandra A wrote:

    There is a bad mistake in the article above about bleach with the water (at least on my screen it appears to say to put “4” TSP of bleach to a gallon of water. I believe they meant 1/4 (one fourth) teaspoon. 4 tsp of bleach in 1 gallon of water is NOT safe.. The article goes on to say “1” Teaspoon for 5 gallons. Please take note.

    Also note there is a safer alternative to bleach on the market: Water Preserver. Look into it.

    The item I have is the Aqua Pail. You can look it up on Youtube.

    September 15th, 2014 at 7:42 am
  10. Bubba wrote:

    A company called lifesaver invented a filter that removes particles down to 15 nanometers, which is smaller than viruses. It is used in disaster areas. Although expensive, one filter can treat 4,000 liters of water. I have one in my closet and don’t have to store water. Check it out.

    September 15th, 2014 at 9:43 am
  11. Doc wrote:

    Sawyer also makes filters that remove even viruses and are good for 1 million gallons. The best I have found.

    September 15th, 2014 at 10:44 am
  12. Franke wrote:

    I own a Sawyer 4-liter dual bag portable ultra purification system. It’s a bag gravity system so doesn’t require any pumping, and purifies a gallon of water very quickly. It uses a .02 Micron absolute hollow fiber membrane purifier, and
    removes 99.997% of Viruses, 99.99999% Bacteria, and 99.9999% Protozoa/Cysts. It’s light, packs small and the filter is rated for one million gallons. I have it as part of my bug out kit. Like most purifiers, it doesn’t remove chemicals though. Some will find it a bit expensive, but since you don’t have to replace the filter, the cost balances out. They have typical 0.2 micron units which cost less.

    September 15th, 2014 at 10:45 pm

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