4 Ways to Make Water Safe to Drink after a Disaster

September 05, 2021

After a major disaster impacts an area, one of the most common dilemmas is a lack of clean drinking water.  The unprepared will likely depend on untreated water contaminated with bacteria, parasites, and viruses.  As a result, many will experience stomach cramps, abdominal pain, and dehydration which can result in death.

This blog will focus on the practical steps you can take now to ensure you can safely treat water.  There are some approaches we will not cover that are a bit more complex such as building a solar still or a natural filter or even pasteurizing water, items we’ll cover in the future.  Instead, we’ll focus on very simple, practical approaches that anyone, even on a limited budget, can safely implement that require little to no knowledge.  I recently did a poll on my channel asking how prepared my community is regarding water for emergencies and 40% responded that they are not ready, so we’ll keep this video to the basics that anyone can apply today, right now.  If you haven’t already begun to build a supply of water, I encourage you to check out some of the other videos I’ll post in the cards above and in the description section below.  This video will not cover water storage, but rather how to make water safe to drink.

A Note About Water

This blog will cover processing water whether you’re bugging out and on the move or at home.  When collecting water to drink for purification or filtration (2 distinct things we’ll cover momentarily), always collect the clearest water you can from moving sources.  This will significantly reduce the bacterial, virus, and protozoa load in the water.  Even flowing water will not be free of foreign, harmful elements or pollution.  Whatever water treatment and filtration method you choose, it is always more effective to combine a filtration and treatment method and to wait the full amount of time required to allow the treatment to reach its full effect. 

Each of these points we cover in this video is easy to follow, relatively inexpensive and should be a part of your preps and knowledge you acquire.  I’ll also put links in the description and comment section below if you want to check out anything we cover along with a link to the notes from this video.

Before we jump into these methods, there are 2 primary ways to make water safe to drink: filtration and purification.  Filtration is the process of cleaning water of impurities removing sediment and most (but not all) microorganisms.  Purification on the other hand focuses more on removing impurities from water such as viruses, chemicals, and other smaller contaminants that filtration can not achieve.  Ideally, when approaching water, we want to use a combination of filtration and purification.  Let’s explore this more in the first point.

1- Commercial Filtration

What I call commercial filtration includes all types of individual water filters you can purchase.  These can range in price, method, and micron filtration level.  Before we cover the various options, let’s quickly cover a few important points to ensure you understand your options.  

Let’s start with first discuss a micron.  A micron is a unit of length equal to one millionth of a meter or .0000393 inches which as you guessed, is incredibly small.  Some of these parasites that can kill you may be as big as 50 microns down to 0.06 microns.  To give you context, human hair is about 70 microns in width.

Okay, so now that we’ve covered microns, let’s utilize that information when discussing water filters.  When looking at water filters, you’ll typically see information regarding the pore size of their filters.  Obviously, the smaller the pore size, the smaller the contaminant it can filter out.  After a disaster, your 3 biggest concerns for water-borne illnesses are bacteria, protozoa, and viruses.  Bacteria cells range from 1 to 10 microns.  Protozoa which are larger than bacteria, like the kind that can cause malaria or dysentery, can be as small as 2 to 50 microns in diameter.  Viruses are much smaller than bacteria and protozoa at 0.06 to 1.4 microns.  Due to their extremely small size, most entry-level water filters will not filter out viruses due to their small size and by so using one of the other treatment methods we’ll cover momentarily in this video combined with filtration, you greatly increase your probability that the water you drink will not make you sick.  It is rare that you’ll deal with viruses in water in the wild which is why most of these entry level filters are marketed to backpackers, but not entirely impossible.  But when a disaster strikes a region, the likelihood of viruses contaminating water sources in an urban or suburban environment is much higher.  Armed with this knowledge, when looking for a personal filtration device, consider these 5 things: the size of particle filtration in microns which we just covered, the weight of the unit, the amount it can filter, the time it takes to apply the filtration, and of course, the cost.  Let’s look at entry-level water filters by starting with 2 primary options: portable and stationary.  

Portable water filters

The options on the low end of pricing along with chemical treatment will ensure after a disaster, you can properly process water to make it safe for drinking.  I’ll start from the low end and move up in price.  

The first is a MiniSawyer.  This is popular among backpackers as it filters down to 0.1 microns and weighs just 2 ounces.  It can filter up to 100,000 gallons of water and the flow rate on these is on the low end coming in at a little over $20.  Of the portable, entry-level options, this is my personal favorite. 

The next option is the Lifestraw, a personal filtering straw.  These filter down to 1 micron and also weighs about 2 ounces. These can filter up to 1,000 gallons and they come in at around $15.  Like the mini-sawyer, their flow rate is on the low end.  These are also geared more toward personal use and not something a group would be able to collectively utilize. 

The next option is a water filter with a gravity bag.  If you are in a temporary location and not on the move, a place where passive filtration can be accomplished in larger quantities, I would recommend this option.  This particular example from Lifestraw can filter down to 0.2 microns, up to 500 gallons, weighs just 6.9 ounces, and will allow you to filter more than 7 gallons per hour.  That will be sufficient for a small group that has banded together after a disaster.  At a little over $42, this is a great option for filtering water quickly and easily.

The last option we’ll cover for entry-level, portable water filters is a Katadyn Vario water filter.  They filter down to 0.2 microns, weigh 1.66 pounds, have a flow rate of 2 liters, or about half a gallon per minute.  They are a bit more on the expensive side at around $75, but the advantage of these is that they include a replaceable carbon core that reduces chemicals, pesticides, and bad taste in water, something the other options can not do.

One note about running water through these filters.  If you’re obtaining water that is not clear and muddy or has any sediment in it, you should definitely consider pre-filtering it.  By introducing sediment into your filter, you shorten the life span of the device.  While not a comprehensive list, a few simple household items you could use to pre-filter the water are a coffee filter, bandana, or t-shirt.  

Stationary water filters

For larger, stationary options that are at or under $300, there are 2 primary choices: gravity and forced.   For gravity filtration, one of the go-to’s within the prepper community is the Berkey water filter.  I have used a home Berkey for years to filter out chemicals from tap water.  They can filter down to roughly 0.2 microns but come in at a much higher price than the portable filters at around $300 to $400 depending on the options you want.  They can process several gallons of water per hour depending how many filters you have and can also remove various chemicals as well.  I’ve had one for 5 years and still use it on a daily basis.  

For a true grid down, post-SHTF scenario, if you need to filter larger quantities of water at a time, you may want to consider a forced filtration system like a PortaWell.  While rapid forced filtration isn’t new, the really great thing about the PortaWell is that you can interchange the filters with ones you can pick up at your local hardware store.  I’ll do a review of this product shortly and you can check it out in the meantime at cityprepping.com/portawell

2- Boiling

Boiling is the best method for rendering dirty, raw water drinkable.  Bringing water to a rolling boil for one minute effectively kills or inactivates protozoa, bacteria, and viruses.  Before boiling the water, if it is cloudy, let it settle and filter it through a clean cloth or coffee filter as we discussed a moment ago.  In addition to destroying pathogens and microscopic organisms in the water, it can also boil off impurities and pollutants that are lighter than H2O, but not all of them such as heavy metals, salts, and most other chemicals.

Bring the water to a boil and let it roll for at least a full minute.  When it cools, you can pour it into clean containers.  As with any method described here, even your boiled water will be better if you can combine it with filtering.

The biggest downside with boiling water is the energy required to do so which may be difficult to come by after a disaster.  If boiling over a fire, you’ll alert others as they can see the smoke or fire.  In order to keep the energy required to accomplish this and the smoke to a minimum when using sticks and other biomass material you can easily find after a disaster, one of my favorite options is the Kelly Kettle. I have reviewed these in the past and I’ll post a link in the cards above and the description section below.  I like the Kelly Kettle because it uses very little material and can achieve a boil of a little over 40 ounces of water in mere minutes.  For the purposes of boiling to make water drinkable, it is the easiest to use I have seen.

3- Chemical Treatment

People have been treating water in the wild with various chemicals for years to render it drinkable.  Bleach, hydrogen peroxide, sodium hypochlorite, chlorine dioxide, calcium hypochlorite, and iodine are common additives.  They all work to neutralize pathogens in the water.  Some can leave a slight chemical taste behind that sometimes fades with time.  Hikers and deployed military have used chemical additives for years to neutralize pathogens in wild water.  

Of the many different types, iodine, hydrogen peroxide, and potable aqua water purification tablets I think are the simplest.  Iodine and hydrogen peroxide you probably already have on hand in your medical kit.  If using a 2% tincture of liquid iodine, add five drops per quart or twenty drops per gallon.  You should wait at least 30 minutes before drinking to let it do its work.  Feel free to agitate the liquid a bit.  If you are using hydrogen peroxide, use two tablespoons per gallon.  It is said to wait 24 hours before drinking.  Regarding the potable tablets, just follow the printed instructions on the bottle.

The best thing about chemical additives is that you can carry enough to purify gallons and gallons of water in a tiny container.  You can use it when you get to your bug-out location, as well.  A one-pound bag of calcium hypochlorite, for instance, can treat 10,000 gallons of water.  I recently did a video explaining how to make bleach with calcium hypochlorite which I’ll link to in the cards and description section below.  Even a simple bottle of additive-free bleach can be used to kill pathogens.  It’s a little like drinking pool water, but it will work in an emergency to keep you safe from pathogens that can kill you.

4- Light Treatment

Using a UV light on a pen or in a bottle is a new, popular way to render pathogens harmless.  I have to admit they are pretty cool.  All you have to do is stir the light in the water or place it in the bottle with the light built-in, and the UV light emitted will neutralize the pathogens.  Rather than removing biological contaminants, including viruses, bacteria, and protozoa, they kill their DNA so they can’t reproduce if you do ingest them.  Ultraviolet water purifiers do not neutralize or remove mineral contamination or pollutants, either.  There are three types of UV light, A, B, and C.  C band wavelengths are the most lethal to organic matter.  

The downsides of this technology are that they are going to be heavier and bulkier.  They are more expensive, starting at about 60 dollars and going up from there.  Like any technology, they are susceptible to breaking, and they are going to require a power source to charge or recharge.  If you can afford the fancy gadgetry and you have the means to keep it charged on the go, this can be a viable option for making raw, natural water drinkable.

In a truly desperate situation, some UV exposure to water can be accomplished merely by putting it in a clear container and placing the container in full sun.  That won’t neutralize everything, as some protozoa may not like sunlight, but being in the sun won’t kill them.  What is happening with the transparent container is part UV light treatment and part pasteurization.  I’ll cover pasteurization in a future video.  However, it is not very useful as the sole water treatment method, and this process takes prolonged exposure to the sun.  Far more effective is a UV device specifically made for water purification.


You can live about three days without water, but your body can begin to suffer from dehydration within a day.  Whichever of the four techniques you choose to use here, hopefully, it will be enough to keep you hydrated to survive after a disaster.  Drinking raw, dirty water might not kill you right away, but it definitely can make you violently ill or get you sick enough to lose fluids as the body tries to flush the alien invaders.  The subsequent dehydration can certainly kill you.  Combining one or more treatment techniques increases the effectiveness of your purification.  At the time of recording this video, Hurricane Ida has just hit Louisana and many parts of the state’s infrastructure, including water, is offline.  If you woke up tomorrow and turned on the water and nothing came out of the sink, would you know how to process water to make it safe to drink?  I hope this video gives you a solid starting point.

I would love to read in the comments what you use to purify your water when in the outdoors or what you have packed in your bug-out bag for when the need arises.  

As always, stay safe out there.

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