Best Practices for Drinking Water Purification in an Emergency

Best Practices for Drinking Water Purification in an Emergency

What happens when there is a boil-water alert, storm, or other natural disaster that disrupts your clean water supply?


There is a range of contaminants that could be in your drinking water. Reducing these improves the quality of your drinking water. 

To clarify terms for this discussion, to filter water is to pass it though a screen, or adsorption medium that physically or chemically removes chemical or physical contaminates. To purify, or sanitize water, is to inactivate the microbiological hazards of bacteria, protozoa, and viruses to a level that will not harm a human (usually at least 99.9% reduction.)

Toxic chemicals in your water are unhealthy to consume. There are a lot of minerals that are healthy, but anything else should be reduced with a carbon filter. Things like chloramines, lead, mercury, VOCs, and pesticides should be removed as much as possible through chemical adsorption, usually with carbon filters.

Bacteria, protozoa, and viruses in your water at high enough quantities will make you sick. These need to be reduced to very low levels to make water consumable for drinking water.

Sediment, turbidity, and organic particles in your water are unpleasant to drink, and may interfere with sanitizing methods. These should be removed with sediment filters, much the way a screen door keeps out bugs.


Depending on if you have Chemical, Microbiological, or Physical contamination of your water there are a range of ways to filter, purify, and sanitize water to make it safe, healthy, and delicious to consume, even in an emergency situation.

Depending on a person's size, activity level, and environmental conditions, a person needs 1 to upwards of 4 gallons of water per day. Plan for this amount based on conditions and group size. This does not include water for washing or cooking.


Boiling water inactivates all microbiological hazards from your water. Bring water to a boil for one minute to ensure full sanitization of water. If it is not possible to achieve a boil with available heating methods, achieving 145 degrees for 5 minutes will pasteurize water and make it safe for human consumption. Keep in mind that this method requires a fuel, or electrical supply, which may be compromised in an emergency.

When using this method, if for some reason there is sediment in the water, it is important to first filter the water through a filter medium to remove as much of the sediment as possible*. By adding chlorine (bleach) in small quantities to your water you can inactivate bacteria, protozoa, and viruses and make your water safe from these microbiological hazards. A good rule of thumb is to add 8 drops of (5-8% hypochlorite) chlorine bleach per gallon of water. Stir, and let the water stand for 30 minutes before consuming.

*Excess sediment in the water will absorb the chlorine, and leave less chlorine in the water to inactivate microbes. Additionally chlorine can combine with other contaminates to make harmful chloramines.

There are a few portable devices available that use UV light to sterilize. UV light rays break up the DNA of cells, and make it impossible for bacteria, protozoa, and viruses to reproduce. It is important to follow the directions of your device relative to volume of water treated, and exposure time, because UV needs adequate intensity to inactivate microbes. Follow the directions for your device carefully. Also, remember that particles and sediment in the water can block the UV rays, so filter your water, or allow particles to settle prior to using UV treatment.

In a pinch, UV from sunlight can be used to treat water. Allow your water to sit in a clear container in sunlight for as long as possible to have UV from the sun inactivate microbes.

One way to provide for purified drinking water in a disaster is to store it before the disaster occurs. By filling drinking water safe containers with drinking water ahead of time, and storing it with food supplies for future use in a safe location, you will be prepared with drinking water for your family. Keep in mind that one person needs 1-3 gallons of water per day. As a back up, it may be wise to have a way to filter and purify this stored water in case it becomes contaminated. Also it is a good idea to periodically check the condition of stored water, and change the water in the containers to make sure water in storage is not becoming contaminated.

There are a range of filtration and purification devices on the market that are intended for backpacking that can be useful on a small scale in an emergency. Look for devices that feature hollow fiber filtration to 0.2 microns and reduce bacteria, protozoa, and viruses by 99.99% to ensure highest levels of drinking water safety. These make great backup and short term water treatment solutions for individuals. If you plan to rely on one of these devices, make sure you know how to use it, and have spare consumable filters that the system requires.


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