Compact Water Purification Straw (at least 0.1 micron filter)
In addition to my other post on boiling water, ideally in a metal container, it is important to be able to quickly and easily access clean potable water without contaminants.
There are a number of brands (LifeStraw, Sawyer, Katadyn, MSR, Survivor Filter, GRAYL) which filter down to 0.1 microns. The Survivor Filter in particular, can filter down to 0.05 microns. 0.05 microns is small enough to eliminate a number of viruses, and not just bacteria or protozoa and other nasty floaties. As a rule of thumb: typically viruses are not found in the woods, like in a camping scenario, but bacteria and protozoa/cysts are. Viruses in water are found in more populated urban areas, where there is greater possibly of pollution from human settlement – this would include farmland areas and cities.
Filtering is done either through gravity, or through manually applying pressure, but essentially both push the dirty water through a filter to cleanse it of impurities.
You can always boil water to guarantee that it is germ-free and safe to drink, but water purification straws are meant for FAST water consumption, which is when you are either constantly on the move, or need to be able to do things quickly and efficiently, like in a bug-out situation.
With straw-style filters, add a flexible 3 to 4 foot clear hose purchased from a hardware store, if it doesn’t come with one. This will allow you to drink water without having to bend over close the ground. Otherwise, pack 2 plastic bags: one for the dirty water and the other to capture the clean filtered water and improvise a gravity fed system. This way you can scoop or fill up one bag with the dirty water, then filter the water into the second bag. That will save your back and gives you the option to move to a more convenient location to purify the water.
For a backup, a zip-lock bag with water purification tables is an excellent and very light-weight addition to a bug out bag kit.
Remember, a typical 200lb male needs about 1 gallon or 3.75 liters of potable water to drink each day, to stay properly hydrated from moderate activity (like walking). Drinking water allows a person to think clearly and be less agitated.
The simple formula for your minimum daily water requirement is calculated as follows:
Water (in liters) to drink a day = Your Weight (in kg) Divided by 3 (then Divided by 10)
(and round up to the nearest full or 1/2 liter)
or
Water (in liters) to drink a day = Your Weight (in pounds) Multiplied by 1.5 (then Divided by 100)
(and round up to the nearest full or 1/2 liter)
Example 1: a 120lb or 54.5kg female would require 1.8 liters (rounded up to 2 liters) of water per day
Example 2: a 210lb or 95kg male would require about 3.2 liters (rounded up to 3.5 liters) of water per day
APRIL 2021: My current water filtration system that I’m using is the GRAYL Geopress 24oz version.
Canadian Prepper recently put out an exhaustive video on how to best collect water from various sources.