How Do I Filter or Purify More Water During or After a Disaster?

How Do I Filter or Purify More Water During or After a Disaster?

Essential Survival Skills

When you encounter any found water, there's always a potential risk of contamination. Therefore, it's crucial to have the means to filter and disinfect it before consumption. Understanding the difference between filtering and purifying water is essential for safe drinking.

Filtering Water

Filtering water involves removing harmful or potentially harmful substances. This includes debris, insects, and dirt, which must be filtered out to avoid unpleasant and unsafe drinking experiences. Advanced filtration systems can even remove microscopic contaminants, such as bacteria, which can cause illness.

Purifying Water

The term "purification" is often used incorrectly. Most devices and techniques labeled as "purifiers" actually disinfect water rather than purify it. True purification would mean breaking water down to its basic components: two parts hydrogen and one part oxygen. In reality, what we achieve is disinfection, which involves killing or neutralizing harmful bacteria and organisms rather than removing them completely.

For safe drinking water, both filtration and disinfection are necessary to ensure you remove harmful substances and neutralize any remaining pathogens. Always be prepared with the appropriate tools and knowledge to handle water safely in survival situations.

Importance of Pre-Filtering

Pre-filtering water is a crucial step before any micro-filtration or disinfection process. This initial filtration removes visible sediment and debris, enhancing the efficiency and effectiveness of subsequent purification methods.

Simple Pre-Filtering Techniques

  1. Bandana Method: Pouring water through a bandana can serve as a basic pre-filter.
  2. Coffee Filters: A more effective option is using coffee filters to trap smaller particles.

Advanced Pre-Filtering Station

For more thorough pre-filtering, consider setting up a multi-layer filtration station:

  1. Layer of Sand: First, pour water through a layer of sand to catch larger debris.
  2. Crushed Charcoal: Next, filter through crushed charcoal to remove finer particles and some impurities.
  3. Coffee Filters: Finally, use one or two coffee filters for an additional layer of filtration.

Sedimentation Method

An alternative method involves allowing the water to sit undisturbed in a jar for about an hour. This process lets sediment and debris settle at the bottom. Carefully pour out the clear water, leaving the sediment behind.

Final Steps for Safe Drinking Water

After pre-filtering to remove visible debris, the water should undergo further purification. Use a commercial water filtration system or apply another disinfection method to ensure the water is safe for consumption.

Disinfecting Method 1: Commercial Water Filtration Systems

The simplest and most reliable way to convert questionable water into drinkable water is by using a commercially manufactured water filtration system. Among the top brands are Berkey and Aquamira, offering a variety of sizes and capabilities, from pocket-sized units to larger tabletop versions. Although these systems can be expensive, they are worth the investment due to their effectiveness.

Ceramic Filters for Comprehensive Filtration

Many of these filtration units utilize ceramic filters that effectively remove nearly all contaminants, excluding heavy metals. Smaller units, such as those in water bottles, use proprietary filters made from various materials. These filters reduce over 99% of harmful organisms and spores, though they are less effective against chemical pollutants.

Portable Filtration with LifeStraw

Another portable and affordable option is the LifeStraw. This device filters approximately 250 gallons of water before needing replacement. To use it, simply place the straw in the water and drink through it. The internal filters eliminate 99.9% of waterborne pathogens and cysts. Measuring around nine inches and weighing about two ounces, the LifeStraw is highly portable and costs around twenty dollars on websites like

LifeStraw Family for Larger Needs

The LifeStraw Family is a larger, yet still portable, unit designed for filtering higher volumes of water. It filters 99.9% of harmful contaminants (excluding chemicals and heavy metals) at a rate of nine to twelve liters per hour. This system features a two-liter bucket for raw water, which flows through a hose and membrane filter to a tap for filtered water. Priced around eighty dollars, it is ideal for families or small groups.

Big Berkey Filtration System for Maximum Capacity

For those needing even greater capacity, the Big Berkey Filtration System is an excellent choice. Though it costs a few hundred dollars, it filters approximately three gallons of water per hour. Utilizing ceramic filters, it removes nearly all contaminants, including pathogens, cysts, parasites, chemicals, and heavy metals. Its effectiveness is so high that it can even remove food coloring from water. The Big Berkey is a sound investment, particularly for families.

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Disinfecting Method 2: Boiling

To ensure the elimination of harmful organisms, boiling water is the most effective method. Experts differ on whether bringing the water to a rolling boil is sufficient or if it should be boiled for several minutes. To err on the side of caution, it's recommended to maintain the boil for a few minutes if possible.

Using a Water Pasteurization Indicator (WAPI)

A reliable way to confirm that water has reached a safe temperature for pasteurization is by using a Water Pasteurization Indicator (WAPI). The WAPI is a sealed transparent plastic tube containing wax. When placed in heating water, the wax melts once the water has reached a temperature high enough for pasteurization, indicating that the water is safe to use.

Alternative Heating Methods During Power Outages

In situations where your electric range is inoperable due to a power outage, there are various alternative methods to heat water. These include:

  • Charcoal Grills

  • Propane Grills

  • Camp Stoves

  • Campfires

These methods can effectively bring water to a boil, ensuring its safety for consumption.

Disinfecting Method 3: Water Purification Tablets & Water Pouches

When boiling water is not an option, perhaps due to a lack of fuel or the need to conserve fuel, water purification tablets are an effective alternative. These tablets can be easily found online or at major retail stores that stock camping supplies.

Water purification tablets are user-friendly, with clear instructions provided on the bottle. They employ one of two main chemicals for disinfection:

  • Iodine-Based Tablets: These may leave a distinct taste in the water. To improve the flavor, you can add a powdered drink mix after disinfection.

  • Chlorine Dioxide Tablets: These typically result in a cleaner taste.

Water Pouches Emergency

Water pouches contain purified water with a 5-year shelf life, ensuring you have a reliable source of clean drinking water in emergencies.

The water is purified using reverse osmosis, a method that exceeds U.S. Pharmacopoeia standards. This ensures the water is free of impurities and safe for consumption.

Each pouch is sealed with a leak-proof design to prevent contamination and bacteria growth. The durable material can withstand extreme temperatures, ranging from freezing (40°F) to boiling (230°F).

Buy: Mayday Water Pouches

These pouches are U.S. Coast Guard approved, making them a trusted choice for emergency preparedness kits and survival gear.

Disinfecting Method 4: Iodine Tincture

Iodine tincture is an effective method for disinfecting water. You can find small bottles labeled as 2 percent iodine at most pharmacies or discount retailers in the USA.

Steps to Disinfect Water

  1. Determine the Amount of Iodine:

    • For clear water: Use 5 to 7 drops of iodine per liter.

    • For cold or cloudy water: Use 8 to 10 drops per liter.

  2. Mix the Iodine:

    • Stir or shake the water to ensure the iodine is thoroughly mixed.

  3. Wait:

    • Let the water sit for 30 minutes to allow the iodine to disinfect it.

Tips for Improved Taste

Iodine may impart a slight bitter taste to the water. If this taste is too strong, you can mask it by adding a powdered drink mix after the disinfection process.

Disinfecting Method 5: Bleach

To disinfect water effectively, use non-scented chlorine bleach with a concentration of 5.25% to 8.25% chlorine. Most store-bought bleach falls within this range. Follow these steps:

  1. Dosage: Add five drops of bleach per liter of water (¼ teaspoon per gallon).

  2. Mix: Stir or shake the mixture thoroughly.

  3. Cold or Cloudy Water: Double the dosage if the water is extremely cold or cloudy.

  4. Wait Time: Let the water sit uncovered for 30 to 60 minutes to allow the chlorine gas to dissipate.

  5. Check for Chlorine Scent: A faint smell of bleach should remain. If not, repeat the process.

Shelf Life

Bleach has a limited shelf life. After opening, it remains effective for about six months. After that, its potency decreases. For long-term water purification, consider making a homemade bleach solution using calcium hypochlorite.

Making Bleach at Home with Calcium Hypochlorite

Calcium hypochlorite, commonly known as "pool shock," is available at pool supply stores for around five dollars per pound. Avoid products with added fungicides or similar chemicals.

Preparing the Shock Solution

  1. Mixing: Add ½ teaspoon of calcium hypochlorite to a gallon of water. Mix thoroughly with a wooden or non-metallic spoon.

  2. Dilution: Do not drink this concentrated solution. Instead, use it to purify water in a 1:100 ratio. Here’s how to dilute it:

    • 1 pint shock solution to 12.5 gallons of water

    • 1 cup shock solution to 6.25 gallons of water

    • ½ cup shock solution to 3.125 gallons of water

    • 4 tablespoons shock solution to 1.5 gallons of water

  3. Mix Thoroughly: Pour the mixture between containers to reduce the chlorine scent.


  1. Corrosion: Calcium hypochlorite will corrode metal, so store it in plastic containers and use wooden spoons for mixing.

  2. Storage: Keep it away from petroleum products to prevent spontaneous ignition.

  3. Shelf Life: Keep the granules dry for indefinite shelf life. A small one-pound package will suffice for long-term needs.

Disinfecting Method 6: UV Light

A relatively new method for consumer water disinfection is the use of ultraviolet (UV) light. This technique offers a quick and easy way to disinfect a liter of water in approximately one minute. A UV portable water purifier is used by placing the end of the device into the water, pressing a button, and releasing a burst of UV light that kills any contaminants present.

Popular UV Purification Products

There are various UV water purifiers available on the market, with SteriPEN being the market leader. While these products are highly effective, they can be expensive. It is crucial to read the packaging carefully and ensure you have the necessary batteries for your chosen unit.

DIY Solar Distillation (SODIS)

For those who prefer a do-it-yourself approach, the same UV technology can be applied through Solar Distillation (SODIS), though it takes considerably longer. Here’s how to do it:

  1. Materials Needed: Clear (not green) plastic bottles and a dark surface.

  2. Process:

    • Fill a clear plastic bottle with water.

    • Lay the bottle on its side in direct sunlight, preferably on a dark surface.

    • Ensure the skies are fairly clear for optimal UV exposure.

Time Required for SODIS

  • Clear Skies: Approximately eight hours to purify the water.

  • Cloudy Skies: Up to two days for purification.

You can purify water in bulk by lining up several bottles at once. Placing the bottles on their sides maximizes the surface area exposed to the sun. The dark surface absorbs the sun’s heat, which, combined with UV rays, helps purify the water.

Ideal Locations for SODIS

In urban areas, the best location for SODIS is on the roof of an apartment building to minimize shade obstructions as the sun moves across the sky.

Does All Water Need to Be Disinfected Before Use?

Essential Water Disinfection

Any water intended for consumption, food preparation, teeth brushing, or dishwashing must be disinfected. This ensures it is safe to ingest and use in food-related activities.

Exceptions for Non-Consumable Uses

Water for sponge baths, washing clothes, or cleaning non-food contact surfaces does not require disinfection. However, it is advisable to filter this water to remove visible impurities, such as floating debris.


Prioritize reserving your stored water and disinfected water for essential consumption purposes. Water is vital for survival, particularly during and after a disaster. Ensuring access to a safe, potable water supply is crucial.

SourceUrban Emergency Survival Plan: Readiness Strategies for the City and Suburbs

Aqua Literz Emergency Drinking Water  - Pallet of 900 liters

Buy 10-Year Shelf Life Water Pallet

Buy Berkey Countertop Water Filter System




Crown Berkey Water Filter

6 Gallons (22.7 L)


Imperial Berkey Water Filter

4.5 Gallons (17 litres)


Royal Berkey Water Filter

3.25 Gallons (12.3 L)


Berkey Light Water Filter

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Big Berkey Gravity-Fed Water Filter

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Travel Berkey

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Black Berkey Replacement Elements


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