SHTF blog – Modern Survival

Weighing the Options for Drinking Water

Water is one of the basic needs for every prepper.  But, does every prepper know exactly what they are guarding against and how to best deal with all the pitfalls? I think some people hesitate because it’s a life or death thing and they don’t want to make a mistake. So let’s take an in-depth look at water purification.

Boiling, filtering, chemicals, and solar are all purification methods that a good prepper should know about. Let’s define all of those first, so we’re all on the same page. Then pros, cons and the limitations.


Boiling of course refers to bringing the liquid to a rolling boil. For most bacteria and viruses the temperature of water at a rolling boil is enough to kill after a minute. If anyone has ever told you it has to boil for 10 minutes, they didn’t know what they are talking about. It does take a frustratingly long time to get cool enough to drink, so keep that in mind unless it’s the middle of winter. Or unless you’re aiming for soup.  If aiming for soup, let that water boil, BEFORE adding in the soup components.


Filtering means running the water through some kind of filter. There are all sorts of porous materials that will work to filter water. Some, like bandannas or socks will only filter out bugs and sand.  Some, like filters available from hyperflow-Microfiltercamping stores (sizes between 0.1 and 0.4 microns,) will remove bacteria from water but will not remove viruses. New “hollow fiber” technology can remove viruses. “Reverse osmosis” filters remove bacteria and viruses and can also remove salt from water, which is important for those dwelling near or on an ocean. No filter can filter out chemical contamination, except activated charcoal, see below..

Common micro-organisms and the filter size needed:

OrganismExamplesGeneral SizeFilter TypeParticle Size Rating
ProtozoaGiardia, Cryptosporidium5 microns or largerWater filter1.0–4.0 microns
BacteriaCholera, E. coli, Salmonella0.2–0.5 micronsMicrofilter0.2–1.0 microns
VirusesHepatitis A, rotavirus, Norwalk virus0.004 micronsWater purifierto 0.004 microns

There are two basic types of filters :Membrane Filters use thin sheets with precisely sized pores that prevent objects larger than the pore size from passing through. Plus: Relatively easy to clean. Minus: They can clog more quickly than depth filters. Depth Filters use thick porous materials such as carbon or ceramic to trap particles as water flows through the material. Plus: Can be partially cleaned by backwashing. Activated carbon filters also remove a range of organic chemicals and heavy metals. Minus: Rough treatment can crack the filter, rendering it useless.


Chemicals refers to what you can add to water to kill the bad stuff but not kill yourself. The most common is bleach. Liquid Chlorine bleach is what most people have on hand. (Clorox or Purex.) Don’t use any bleach with perfumes or dyes or other additives, you don’t want to be drinking that stuff.  Place the water in a clean container. Add the amount of bleach according to the Department of Health table below. Mix thoroughly and let stand for at least 60 minutes before drinking. Remember that chemical treatment of cloudy water is less effective, so filter your water first to get it as clear as possible. Iodine is another chemical used. Some people are allergic to iodine though, so be aware of that. Bleach will not kill some disease-causing organisms commonly found in surface water. Bleach and Iodine will not remove chemical pollutants.

Treating water with household bleach containing 5.25-8.25 percent chlorine
Volume of Water to be TreatedBleach Solution to Add
1 quart/1 liter5 drops
1/2 gallon/2 quarts/2 liters10 drops
1 gallon1/4 teaspoon
5 gallons1 teaspoon
10 gallons2 teaspoons


Cheapest of all, sunlight can be used to purify water. It harnesses the UV rays and the heat. Clear plastic bottles placed in the sun for 6 hours will kill off bacteria, viruses, protozoa and worms.  But of course, not chemical pollutants. Like the other purification methods, it works best on filtered water.  Minus: Doesn’t work at night or on cloudy days.   Need more on this one? Check out the 88 page manual!

I’d say for the best outcome, you’ll thank yourself if you have close to a week’s worth of safe drinking water stored, and the makings to set up one of these methods in  day or two. If you’re not storing rain water, you’ll need to scout out the local creeks/rivers/ponds/etc.

Don’t let this basic need trip you up when it matters most! Find the method that works for your situation and get it set up! Anyone with some water stories to share? Shout out in the comments.

– Jennie Erwin

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