Home » 5 Methods to Purify Drinking Water In Emergencies

5 Methods to Purify Drinking Water In Emergencies

Bleach is a simple method to purify your drinking water in an emergency. If you don’t have a method to boil water for disinfection or large quantities of water need disinfecting it is the best choice for cleaning emergency drinking water.

If you are nervous about using Clorox to clean your water, know that federal agencies like the Federal Emergency Management Agency (FEMA) recognize bleach as an emergency method for disinfecting drinking water.

In Emergencies, household Clorox Bleach can be used to purify or disinfect drinking water but there are limitations. Bleach will not make high-salinity ocean water safe to drink (seawater) and it will not remove contaminants like chemicals, heavy metals, or some parasites.

Household bleach will kill most illness-causing bacteria and microorganisms.

I use bleach to purify drinking water in blue barrels, clean toilets really well, and in a solution to clean and disinfect countertops. Make sure to follow safety precautions on the bottle and wear close you don’t mind ruining. I can’t tell you how many t-shirts and pairs of shorts I’ve ruined by splashing bleach on them.

Scott, Ready Squirrel

This article contains Amazon links. Ready Squirrel receives a cut of Amazon’s profit, at no additional cost to you, when you purchase through our links. We appreciate the money and use it for beans and bullets.

If you can’t get to the store purchase Clorox online.

Amazon| Clorox Store

#1 How To Purify Water With Bleach: 8 Steps

Boy in dirty water

Most municipal water is treated with chlorination which is what you are doing when you treat your water with Clorox or other household bleach. Here are 8 easy steps to disinfect your drinking water.

  1. Collect the water that hasn’t been treated and let it sit long enough for the chunks to settle to the bottom of the container
  2. Strain water through a clean cloth like an old t-shirt or cheesecloth
  3. Pour the strained water into a clean container
  4. Add Unscented Household Bleach  (Water-to-bleach ratios below)
  5. Allow bleach treated water to stand for 30 minutes
  6. Properly treated water should have a slight chlorine odor
  7. If there’s no chlorine odor, repeat the treatment
  8. If repeating the bleach treatment, add the same amount of bleach; wait another 15 minutes.  Check again for the chlorine odor before drinking the water

Bleach has a shelf-life of six months, and then its potency begins to decline. If you aren’t getting the chlorine smell, the bleach may be beyond its expiration date.

Bleach to Water Ratios For Purification

Look at your bottle of unscented household bleach to determine the percentage of sodium hypochlorite in your bleach. The percentage will be used to determine the ratio of water to bleach. See the chart below for ratios.

Chart #1 Bleach To Water Ratios In Gallons

Volume of water
in gallon(s)
1 gal8 drops (.08 tsp)6 drops (.06 tsp)
2 gal16 drops (.16 tsp)12 drops (.12 tsp)
3 gal24 drops (.24 tsp)18 drops (.18 tsp)
4 gal32 drops (.32 tsp)24 drops (.24 tsp
5 gal40 drops (.40 tsp)30 Drops (.30 tsp)
6 gal48 drops (.48 tsp)36 drops (.36 tsp)
7 gal56 drops (.46 tsp)42 drops (.42 tsp)
8 gal64 drops (.64 tsp)48 drops (.48 tsp)
55 gal440 drops (4.46 tsp)330 drops (3.34 tsp)
Emergency Disinfection of Drinking Water: Environmental Protection Agency

Bleach to Water Ratios For Emergency Water Disinfection (qt/ltr)

The following chart gives the ratios, in quarts and liters, of household bleach to water for disinfection.

Chart #2 Bleach to Water Ratios In Quarts

Volume of water
in qt(s) and ltr(s)
6% and 8.25%
1 qt/ltr2 drops
2 qt/ltr4 drops
3 qt/ltr6 drops
4 qt/ltr8 drops
5 qt/ltr10 drops
6 qt/ltr12 drops
8 qt/ltr16 drops
10 qt/ltr20 drops
Compliments of The Nevada Division of Environmental Protection
How To Disinfect Drinking Water

Water Purification Container(s)

Choose water containers that are food-grade plastic or glass that include a cap or a lid.

Food-grade plastic is the best choice because glass breaks easily and does not withstand freezing. In a pinch, you can use 1-liter plastic pop bottles or juice bottles.

Do Not Use These Containers For Water Storage

  • Plastics that aren’t food grade because they can leach harmful toxins into your drinking water
  • Metal containers that can react with certain cleaning disinfectants and release harmful chemicals
  • Containers used to store hazardous materials or non-food grade items
  • Any mystery container where you aren’t sure what was stored in them previously

Check out the Ready Squirrel article, “21 Emergency Water Storage Containers.”

Plastic Water Bottles

How to Clean Containers for Emergency Water

Disinfecting your containers is a simple process, just make sure you clean the inside of your container and your cap or lid well and get all of the bleach out.

  1. Add 1 teaspoon of unscented household bleach to 1 quart of water
  2. Add the bleach solution to the container and shake well
  3. Make sure to coat the entire inside of the container
  4. Let the container sit with the bleach solution for 30 minutes
  5. Pour out the solution
  6. Rinse thoroughly
  7. Remove all of the bleach from the containers

#2 Boiling Emergency Water: 8 Steps

Boiling water is the preferred method of disinfecting water in an emergency because it kills bacteria, viruses, and protozoa. Keep in mind it is more challenging to boil large amounts of water unless you have the necessary equipment. You could use an outdoor propane burner and a huge cook pot to clean larger quantities.

Keep in mind that boiling water will not remove harmful contaminants such as heavy metals, fertilizer, pesticides, radiation, salts, or chemicals. It is suggested you set emergency water aside before a catastrophe like ground flooding, tornadoes, or hurricanes to avoid contamination with chemicals and solvents you can’t remove.

Person boiling water with a jetboil flash

Boiling To Disinfect Water: 8 Easy Steps

  1. If cloudy, let the water settle
  2. Filter through a clean cloth like an old t-shirt
  3. Bring water to a rapid boil
  4. Boil for at least 1 minute at altitudes below 5000 feet
  5. At altitudes above 5000 feet boil water for 3 minutes
  6. Let water cool
  7. Store in a clean container with a cap or cover
  8. To improve the flavor of water add a pinch of salt
Granular Hypochlorite

#3 Granular Calcium Hypochlorite

Typically used to clean swimming pools, you may know calcium hypochlorite as pool shock (HTH.) A 1lb bag can treat up to 10,000 gallons of drinking water, and it has a 5-year shelf life. In comparison, liquid Clorox and other household bleaches have a 6-month shelf life.

Granular Calcium hypochlorite is used to create a chlorine solution to disinfect drinking water. Take calcium hypochlorite and mix it with water to make liquid bleach. This solution is used to treat your drinking water.

The active ingredient used to treat municipal water is often calcium hypochlorite.

Using Granular calcium hypochlorite to treat water will not remove harmful contaminants such as heavy metals, fertilizer, pesticides, radiation, salts, or chemicals.

Treat Water With Calcium Hypochlorite: 7 Steps

Warning: This is a two-part process. First, create a solution of sodium hypochlorite in 2 gallons of water. Second, use the first solution created to treat the water you will drink. You are making liquid bleach in the first part (not to drink!) and treating your water in the second part.

  1. Mix the solution of granules and water in a well-ventilated space, wear eye protection and gloves
  2. Add 1 heaping teaspoon of high-test granular calcium hypochlorite (HTH-pool shock ) to 2 gallons of water.
  3. Stir until granules are dissolved, avoid breathing the fumes
  4. Warning: You are not drinking this mixture you are using it to treat water in the following step.
  5. Add one part of the solution you just made to 100 parts of the water you are treating.
    1. . This is roughly equal to adding 1 pint (16 ounces) of stock chlorine to every 12.5 gallons of water or (approximately ½ liter to 50 liters of water) to be disinfected.
  6. Water should have a slight chlorine smell, if not, treat the water again.
  7. If the water has too much chlorine smell, let it sit, and the chlorine will dissipate or pour it back and forth between clean containers.

Reference: Emergency Disinfection of Drinking Water, Environmental Protection Agency EPA (link below under useful links)

WARNING: Do not breathe the toxic fumes from the pool shock or the treatment solution you make, wear eye and hand protection when using. Store sodium hypochlorite away from flammables, including paper, gasoline, oil, or solvents. Do not store near ignition sources that can cause heat, spark, or flame such as lawnmowers or generators

Calcium Hypochlorite is a strong antioxidant. Follow the instructions on your package for safe handling and storage.

Amazon| Dry Tec Store

#4 Household Iodine

Using the tincture of iodine to treat water will not remove harmful contaminants such as heavy metals, fertilizer, pesticides, radiation salts, or chemicals.

Disinfect Water With Iodine: 5 Easy Steps

Humans need iodine in their diet but too much iodine is poisonous. Iodine comes in tablets, crystals, and liquid forms (tincture of iodine.) If you are using tablets or crystals, follow the directions on the packaging to treat your water.

Following are the 5 steps for disinfecting water with iodine.

  1. Let the water settle if it is cloudy
  2. Strain water by pouring it through a clean cloth like an old t-shirt or cheesecloth
  3. For clear water add 5 drops of 2% tincture of Iodine to each quart or liter of water for disinfection
  4. If water is cloudy or stagnant, add 10 drops of Iodine
  5. Once Iodine is added, stir, cover and let it sit for 30 minutes before you drink it.

If you are allergic to iodine (like eating shellfish), don’t use iodine to treat water.

Amazon| Carlyle Store

#5 Water Tablets To Disinfect Drinking Water

Water Tablets are often used by hikers, backpackers, and outdoorsmen to treat drinking water because they are small, lightweight, and effective. The most common types of tablets used are chlorine dioxide and iodine.

The upside of using water treatment tablets

  • Tablets are useful to store for emergency preparedness.
  • Tablets can be easily stowed in a backpack if on the move, and they build redundancy into your water treatment options.

The downside of using water treatment tablets

  • Chlorine Dioxide tablets take 4 hours to treat water for Cryptosporidium
  • Iodine does not kill the parasite cryptosporidium
  • Tablets can leave a nasty flavor and/or odor after treatment.
  • Some tablets don’t kill Cryptosporidium, which can make you sick. It comes from animal and human feces causing stomach cramps, diarrhea, and intestinal pain

Common Water Treatment Tablets

To use the tablets, follow the directions provided on the packaging. If you are interested in purchasing tables follow the Ready Squirrel Amazon links under “treatment tablet.”

Types of Water Disinfection Tablets:

  • Iodine
  • Chlorine Dioxide
Treatment TabletIngredientPurification TimeWater Purified Per TabletEffective Against Cryptosporidium
Katadyn Micropur MP1Chlorine Dioxide4 hours1 literYes
Aquamira Drops Chlorine Dioxide4 hours1 literYes
Potable Aqua with PA PlusIodine35 minutes1 literNO
AquatabsSodium Chloride40 minutes.75 literNO
Potable AquaChlorine Dioxide4 hours1 literYes

Using Water Disinfection Tablets to treat water will not remove harmful contaminants such as heavy metals, fertilizer, pesticides, radiation, salts, or chemicals.

Information compliments of the Centers for Disease Control and Prevention (CDC)

Emergency Disinfection of Drinking Water, EPA PDF click here

Drinking Water Treatment and Sanitation, CDC click here

Water, Emergency.gov click here

Food and Water In An Emergency, FEMA PDF click here

Leave a Comment