Water in Emergencies: Hazards and Purification

Water is a non-negotiable, high-use consumable. You'll never not need it. Join us to learn about how to treat your water, no matter your situation.

December 30, 2019


Water is the third item on the immediacy checklist for managing emergencies. It comes behind breathable air, and the ability to survive the elements. Even so, it’s arguably the most important when we look at ongoing needs after a disaster, or even while on an outing. Few of our other necessities are as potentially dangerous as water. Water is a vector for bacteria and parasites, as well as potentially toxic dissolved solids and hazardous chemicals. This article will attempt to break the topic into purification, purpose built and improvised filtration methods, and contaminants.

If you have children, this article will be especially relevant; water is a major contributor to childhood mortality.

Why talk about water?

The CDC states that “About 88% of diarrhea-associated deaths are attributed to unsafe water, inadequate sanitation, and insufficient hygiene.” Further, they’ve attributed about 11% of childhood deaths are due to diarrhea globally.

We typically don't talk about it, but this deserves your attention; not only do sanitation related illnesses make you less effective, they risk infecting others. The faster you use up your resources, the sooner you need to focus on finding more, and being ill requires fresh, clean water, as well as things such as antibiotics,.

Further, water is a major source of drowning. Drowning is responsible for more deaths to children aged 1-4 than any other cause, according to the CDC.

As if all that wasn't enough, flash floods are the primary cause of weather-related deaths in the United States, based on government statistics. Because they can strike any region, a cogent assessment and plan for flooding is something that everyone should consider… not just for your home, but for your commute and common routes.

So water needs no introduction, and apart from being vitally important, it is also deadly. What this article is designed to do is dissect three main topics regarding water safety, and describe how to mitigate risk as much as is possible.

The Article will be broken into two parts – first, why we need to filter and purify water, and the mechanisms we use to do that. Second, we’ll take an in depth look at the specifics of the various contaminants, what they do, and where we need to be extra cautious about them.


Water purification means a variety of things. Typically, there are three types of hazards we need to filter out: Biological, Dissolved Solids, and Chemical. When we think of filtration, it’s typically passing water through a fine and coarse filter that traps biological organisms (Bacteria – Viruses are typically too small to be effected by things like sand filters), and activated carbon to bond to free chemicals.

Put simply, the filtration layer’s job is to trap larger, living organisms, while the carbon’s chemical latticework traps chemicals. However, neither do a particularly good job of removing dissolved solids – some of which can be tremendously toxic, such as lead.

There are other methods of filtration as well; Reverse Osmosis, and vacuum filtration, but these techniques typically require electrical power, and/or a laboratory. In addition, they require costly and unique mediums to act as filters – mediums that have limited lifespans or require frequent filter changes, making them impractical for emergency use over protracted timelines.

Primitive/Improvised Solution

The simplest method of water filtration is a sand-charcoal filter. These can be improvised, usually with materials that can be found locally. As mentioned, to prepare this filter, you’ll need a fine layer of sand, and a coarse layer of slightly larger gravel. It’s important to note that “slightly larger” doesn’t mean pebbles or rocks. We are looking for something between sand and pea gravel.

In addition, you’ll need something that keeps the media out of the water – this can be anything from a shirt to a coffee filter. You’ll have to improvise based on your situation – and keep in mind this is a ‘stop gap’ solution to get you safe water, not perfect water.

To make this filter, you’ll need: - Two water containers – if one is metal, and can be boiled, all the better.

- A filter to separate the device from the collecting container.

- Sand, pea gravel, and charcoal.

Assembling your DIY Filter

Assemble the material and make your filter by putting the base layer of charcoal at the bottom – again, make sure you put a filter of some sort between the opening and the collecting container. Improvised plastic bottles work well. Cut some holes in the lid, and wrap a coffee filter over the opening. Fasten it with a rubber band, tape, rope - whatever you have available.

Once the cap is complete, open the rear of the bottle and add in charcoal. This forms your base layer. On top of this, fill the about ½ of the bottle with sand. You should have a couple inches between the sand, and the top of the bottle. Add in about an inch of the pea gravel. From this point, you’re ready to add water to the filter and collect it. Keep in mind, depending on how good your filter is, there may be discoloration to the water. The charcoal will often cause the water to be black, but it won't hurt you. 

However, as a precaution you should now boil it to make sure you’ve killed any biological contaminants not sifted out by the filter itself.

It is inadvisable to drink it without first boiling it, but these filters do a fair job of getting rid of the water-borne hazards.

Backpack Filters

Improvisation gets a lot of attention. People are impressed by resourcefulness, but that doesn't change the fact that it's second rate compared to having the proper gear to begin with. Fortunately, there is a variety of good options that fit neatly in a backpack. Katadyne and MSR make filters that have been tested by the ISG staff, and are “good to go”. While you might incline towards a “straw” design due to light-weight and portability, comparison between these designs and actual filters have shown a major disparity in quality of treated water.

Chances are, you’ll need a water filter before you’ll need a gun, a tactical vest, or other equipment, so make a good filter a priority. If you find yourself in need of clean water, it'll be well worth the price of buying a quality filter.

There's a lot of talk about life-straw or Sawyer type filters, but they come with some signifiant drawbacks:

  • They don’t do a good job of providing rapid access to the water from comfortable positioning. You gotta either hover over the water or shuffle containers. That’s not fun if it’s for real, and your supply of a consumable, reoccurring need resources depends on you doing this. You'll never not need clean, potable water, so it’s not a bad idea to go over ready on your filter.‍
  • It’s really difficult to gather enough water if you’re doing this for more than just a sip for yourself. If you have kids, toss it out and get an actual filter. Further, even if it's just you, a regular filter makes it gathering water a much faster, less vulnerable proposition.‍
  • Hate to sound fussy, but we have not used on that didn’t leave nasty taste when pulling from questionable water. The actual pack filters we’ve tested (Katadyne Hiker pro/Vario, MSR) did much better.‍
  • They also don't hold up well to storage or repeated use, regardless of what their official capacity states.

These devices are reliable enough to 'pump and go'; the amount of bacteria that slips through shouldn’t be enough to upset your system. However, it’s recommended to get to a position in which you can boil the water for maximum safety… especially if you suspect there’s a contamination source (carcass, sewage, drainage from an area with contaminants such as industrial area).

Even so – nothing short of distillation will do an adequate job of removing those pollutants.

Home systems and Distillation

Superior to the above methods are more advanced system, such as home water purification systems and distillation. Home systems generally come with the disadvantage of requiring energy – which requires that your home has infrastructure to function independent of an energy grid. However, the quality of these systems when maintained, is second to none. These systems use complex processes and often proprietary filter media that you can’t replicate by improvisation.

Distilling is incredibly effective in removing dissolved solids, killing organisms, and preventing chemical contamination, and is reasonably straightforward.

Distillation DIY

Distillation works by causing water to change state from a liquid to a vapor. Once the water is vaporized, heavier elements are removed from the molecules, leaving behind a distillate of undesirable chemicals. The vapor is collected and returned to a collection pan, where it becomes safe for consumption. Distillation requires a constant heat source, which in colder climates can be an energy and labor intensive process. In warm, sunny climates, a solar water distiller can be created relatively easily. Many variations exist, but this article on Mother Earth News shows an excellent example of a good design:

You can improvise with items as simple as a plastic bottle:

And this, from glass:

You can likewise purchase premade kits. The principle remains the same: 

1. Force the water to change from a liquid to a vapor 

2. Trap the condensed water 

3. Redirect it away from the chamber in which it initially changes state.

While distilled water has a place, it's important to note that long term consumption of distilled water can actually cause illness, as much needed electrolytes and minerals are absent from distilled water. Especially when the body is under stress, truly distilled water can actually do some harm.


One of the most unsung villains of disaster management is sanitation. For some reason, survival bloggers don't really want to abandon the story line about survivalists weighed down under guns and MRE's to talk about dying from fecal bacteria. Here's the real deal though: it's a serious issue and it demands your attention.

Imagine the following: You're in a situation in which the waterworks have been disrupted. Power is spotty, and no clean water is being pumped into your home. You're doing your best trying to maintain a supply gathered from rain, which you're storing in a bathtub, but there are some problems:

  • There's no reliable power to boil the water.
  • Dishes are hard to wash.
  • There's limited supplies of toilet paper.
  • Without running, clean water, soap can only get you so far.
  • Hand sanitizer can't be used for dishes.

The bottom line in this situation - which is remarkably common and mild - is that bacteria is going to get introduced. When they do, the body's demand for clean water goes way up.

The conditions described above create a self-developing swirl of sanitary problems that you're going to have to head off.

A home water filtration system, made by Rainsoft


As stated above, water contamination is one of the most significant risks for people in places with failing or non-existent infrastructure, and of that contamination, biological infections account for some of the most serious; being biological, the threat is both quick, and easy to mitigate. Boiling destroys most bacteria and viruses, and as we will discuss further, distillation will remove the threat from biological agents entirely. Additionally, hygiene and sanitation play an integral part in preventing exposure to all biological contaminants.

The amount of biological and naturally occurring contaminants is staggering; The following sources detail many of the most dangerous:

Source: Waterborne Diseases

Source: Groundwater Contaminants

Short of having a laboratory to scrutinize your samples for purity, there are very few guarantees that you've completely purified the water in question, and anyone who tells you otherwise is selling something. At the end of the day, here's what you can do:

  • Filter, to the best of your ability, the water you collect. Doesn't matter what you've got, make the effort.
  • Boil, to the best of your ability, whatever water you filter.
  • Store said water in glass bottles in sunlight if possible. The UV alone does a good job purifying water.
  • Plan for more than you'll need. Water is a non-negotiable, high-use consumable. Next to avoiding thermal injuries, it's one of our main priorities.
  • Don't go cheap on your water filter.

The good news is your body is an organism and it's good at fighting. Take this information and build on it to ensure you have the knowledge, skill, and equipment to ensure you and your family have access to safe water, whether on the trail, or in an emergency. Some contamination is to be expected. The key is to ensure that the biological and heavy metal contaminants are dead and gone.



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