Emergency Water Disinfection

 Emergency water is one of the, if not the most, important aspects of preparation. Yet, the focus is often shifted more to food and gear. Food, shelter, equipment...these are important but without water--good, safe water to drink--you will end up dying.

Besides water storage and having the means to filter and purify water, there may be a time when you need to use get emergency water...without the use of a filter.

If you read Red Cross, FEMA, or other disaster assistance organizations they usually don't mention the use of specific backpacking-type water filters. From what I can gather there are a few reasons for this. First, being non-profit and/or government organizations, they are not allowed to endorse a commercial product, so you won’t see them recommending any particular filter.

Another factor is backpacking filters cost money. These organizations want to promote easy, inexpensive methods to obtain clean drinking water. Filters are great to get safe water, but there are other options.

There are three methods that are generally recommended: boiling, chlorination, and distillation.

Boiling Emergency Water

Boiling water is the most common, and probably one of the easiest and safest, methods to disinfect emergency water. The downside is it requires a heat source, and, once boiled, you need to wait for the water to cool down. If you’re cooking food, make sure you have some water that can be boiled. While boiling water on a propane stove may not be able to happen simultaneously as cooking a meal, you can probably add an extra pot, with water, on a cooking fire. That way you’re using the same fire to cook your food, and provide safer drinking water.

Boiling water is sufficient to kill most disease-causing biological contaminants, such as viruses, protozoa, and pathogenic bacteria. However, because some of the water leaves as steam, any other contaminants in the water become more concentrated. A good pre-filter can strain out many of the larger particles. 

Here’s the recommendation for boiling water:

  • If the water is cloudy, let it first settle.
  • Let the water filter through a coffee filter, clean cloth, or other type of homemade filter to remove the larger debris and contaminants from the water.
  • Bring the water to a rolling boil for at least one minute—this is a rolling boil, not just little bubbles. If you’re at a high altitude, above 5,000 feet, boil the water for at least three minutes.
  • Let the water naturally cool down and then store it in clean containers.

Boiled water will taste flat. A couple options to improve the taste is to add a pinch of salt for each quart of water. Taste can also be improved by aerating the water, by pouring it from one clean container to another several times.

Chlorination - Emergency Water

Another method for disinfecting emergency water is to use regular household bleach. If you can’t boil the water, this is a good alternative.

This is important: Do not use color safe, scented, or bleaches that have added cleaners!

Use only regular, unscented chlorine bleach products. The active ingredient should be 6 or 8.25% of sodium hypochlorite. Some sources will state 5.25 to 6 percent. In any case, it should be no less than 5.25 and no more than 8.25 percent. 

The bleach should be stored at room temperature and be less than a year old because it will degrade over time. Unopened bleach can last longer, but the bleach you should use for chlorination should be from an unopened or newly opened bottle. The reason is the potency decreases over time. Unopened bleach will also degrade over time, it will just take a longer than opened containers. Because bleach does lose its strength over time, boiling water is a better alternative. But, if you choose to include chlorination as an option, be sure to rotate your bleach regularly so none of it is more than a year old.

To treat your water with bleach, the following is what is recommended by the United States Environmental Protection Agency, specifically on this web page, which also discusses boiling water: https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water.

First, let cloudy water settle. Filter the water through a coffee filter, clean cloth, paper towel, or other homemade filter to remove larger debris.  

Using a clean dropper (you might have one in the medicine cabinet or emergency kit) and fresh bleach (less than one year old), use the table that follows as a guideline for how many drops of bleach should be added.

If the water is cloudy, colored, or very cold, double the amount of bleach.

Stir the bleach into the water and let it sit for 30 minutes. There should be a slight chlorine smell to the water. If it doesn’t, repeat the dosage and let it sit for another 15 minutes before using. If, after a second treatment, it still doesn’t have a bleach smell, discard the water and find another source.

If the chlorine taste is too strong, pour it from one clean container to another and let it sit for a few hours, which allows for some of the chlorine to evaporate and degrade.

Table of amount of bleach per volume of water. Bleach may contain 8.25% sodium hypochlorite. Taken from https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water


Water volume:                        1 quart (1 liter approx.)

Qty of 6% bleach to add        2 drops

Qty of 8.25% bleach to add    2 drops


Water volume:                        1 gallon

Qty of 6% bleach to add        8 drops

Qty of 8.25% bleach to add    6 drops


Water volume:                        2 gallons

Qty of 6% bleach to add        16 drops (1/4 tsp)

Qty of 8.25% bleach to add    12 drops (1/8 tsp)


Water volume:                        4 gallons

Qty of 6% bleach to add        1/3 teaspoon

Qty of 8.25% bleach to add    1/4 teaspoon


Water volume:                        8 gallons

Qty of 6% bleach to add        2/3 teaspoon

Qty of 8.25% bleach to add    1/2 teaspoon


Distillation - Emergency Water

While chlorination and boiling are options for disinfecting emergency water, distillation is the process where you can get clean water. This process removes biological and other contaminants from the water. It is also the only process that can purify and make salt water drinkable.

To understand distillation, consider nature’s water cycle. Water evaporates into the atmosphere, where it condenses, and then precipitates through rain or snow.

During the evaporation process, which is primarily caused by the sun heating the water (such as the oceans), liquid water turns into vapor. In this process any contaminants are left behind while the pure water vapor rises into the air.

Eventually the water vapor cools and condenses into clouds, which move over land and the water falls to the earth in some form of precipitation. Unless the precipitation—such as rain or snow—is falling through polluted air, the water is pure.

The distillation process is similar. In a closed system (meaning water vapor doesn’t escape), water is heated up and water vapor forms. The water vapor then condenses on a surface, which is collected as pure water.

The Red Cross and FEMA have produced a pamphlet titled, Food and Water in an Emergency, in which a simple emergency still is described. The following image is from page 12 of the pamphlet. 

Simple water distillation using a cup and pot with water. Image from FEMA, retrieved from https://www.fema.gov/pdf/library/f&web.pdf
For the emergency water still, you need a heat source, a large pot with lid, and cup. Tie the cup to the handle of the lid so that the cup will hang upright with the lid upside down. Fill the pot about halfway with water, but not so much that the cup will dangle into the water. Then boil the water for at least 20 minutes. 

In this emergency still, water vapor rises and condenses on the lid, runs down to the handle, and drips into the cup. 

Ideally the lid and handle should be as clean as possible as any contaminants on them could contaminate the condensing water. Using nitrile gloves when handling the lid and prepping the cup can help reduce the likelihood of contamination.

There are commercial water distillers available. If you get one for emergencies it’s better if it doesn’t use electricity for the distillation process.

There are also do-it-yourself options for creating solar powered water distillers.

For more information, check out the United States Environmental Protection Agency's page "Emergency Disinfection of Drinking Water"

World Health Organization - Technical Brief - Boil Water

Making Water Safe in an Emergency, CDC webpage




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