How to Purify Water and Make it Safe to Drink

How to Make Water Safe to DrinkWhen life as we know it stops, aka when the zombies show up, civilization will go downhill very fast.  You have to assume that things we take for granted, like clean, running water, and electricity will be gone in a matter of hours.  Despite your current lifestyle probably being very tech-heavy, you can actually live without electricity.

Water is a different story.

It’s recommended that you drink a bare minimum of 1 liter of water per day in a survival situation just to avoid dehydration.  This amount is much lower than you actually require, and your requirements go up based on the temperature, and your amount of physical activity.  In other words, one of your first thoughts after you evade the zombies should be where to find water.

This is well and good, however water is heavy.  A liter of water weighs approximately 2.2 pounds.  To carry a three day supply in your bug out bag isn’t too bad, even for a family – and especially if you can spread it out among a few people.

If you are in a long-term safe house, such as a bunker or fortified area, you can easily stockpile clean water in every container available while it’s still running.  This will hopefully last you a long while, but even that supply is indefinite.

What this means, is that any way you cut it, you’re eventually going to need to be able to make your own drinking water.  Luckily, there are several ways to do this effectively, although they all have their disadvantages.


Boiling is a great way to make water potable, although it is a bit cumbersome.  You need a container to boil the water in, fuel to feed the fire, and a way to start the fire.  It becomes even more of a hassle if you have a large group and only 1 small pot to boil it in.

It does have advantages, though.  You don’t need a thermometer, because it’s very easy to tell when water is boiling.  It also kills most of the bad shit that might make you sick.

Survival guides and people on the internet recommend various boiling times to make water safe.  Some say 2 minutes is okay, some recommend at least 10 minutes, but 20 is better.  Don’t listen to any of them.

Both the CDC and EPA recommend the following: boil water vigorously for 1 minute, or for 3 minutes if you’re at an altitude above 2000m (6562ft).

More than that is wasteful, you’re expending extra energy maintaining your fire, and losing good water in the form of steam.

Also of note is that by boiling it, you’re already playing it safe!

The truth is, pasteurization occurs at 149º F, well below the boiling point of water.  Also, by maintaining a lower temperature for longer durations, you can achieve pasteurization.  The difficulty is knowing what the temperature actually is.

So, to play it safe, stick to the boiling for 1 minute rule, unless absolutely necessary.



Distilling water is a great way to make it drinkable, and the only way to make salt water drinkable.  In this process, you convert your dirty water to steam, and capture the vapor, leaving behind the impurities.  You then condense the vapor back into pure water.

There are 2 primary ways to do this.

The first, and more difficult in a survival situation, is to build a contraption that you can heat with a fire, and condense the water in cooling tubes.  This is the method used by distilleries and you can view examples here.

The easier way to make this happen is to use a solar still.  The basic idea is that you use the power of the sun to evaporate the water, the vapor condenses on a sheet of plastic (shrink wrap, a trash bag, whatever is handy), and collects in the smaller container.

The biggest benefits of a solar still are it’s versatility, and that the sun does much of the work for you, once it’s built.  The downside is that it can take a lot of effort to build, and possibly to maintain if you need to keep sourcing more water.

Many solar stills start with a hole in the ground, but you can use any large container (if you hole up at Wal-mart, think kiddy pool).  The dirty water can be from a mud hole, salt water, plants, wet sand, or even urine.

For a good illustration of this in action, check out this video.  There are many videos on YouTube, just search for “solar still”.  Everyone seems to have their own method of building one.


Chemical treatments

One of the easier ways to clean water is to add a chemical that is safe for you, but will kill the parasites or bacteria that might be present.  The drawback is that it might not kill everything.  Cryptosporidium is especially tolerant to chlorine disinfection. although not immune.

To treat water, you can use 2 drops of household bleach per quart of water.  This amount is approximately 1/8th of a teaspoon per gallon.

Be wary of the date on the bleach.  It has a shelf life of only 6 months until it starts losing it’s potency.

Another way to treat your water is by using a tablet product.  These generally have much longer shelf lives, maybe up to 5 years.  And, they work in about 30 minutes.



Perhaps the easiest way to get drinking water is to filter it.  This doesn’t mean passing it through a coffee filter though.  You need special equipment, and it’s not cheap.

With that said, you should at least check it out.  The Amazon page description says: “The most rugged, longest lasting microfilter available. Chosen by the U.S. military and expeditions due to it’s extreme durability and dependability. For those who want the best.”

If you go this route, all you have to do is pump the water directly out of the stream or pond, and directly into your canteen or bottle.  Then just clean and maintain the filter.


Other things to consider

  • Collected rainwater or melted snow isn’t necessarily safe to drink just because it didn’t come from a pond or stream.  It should be considered dirty until you treat it.
  • Collection of rainwater in your area might be illegal!  Now, obviously you could give a fuck about the law when the zombies show up, but be wary of your local laws if you’re just testing these practices.
  • Once treated, water needs to be covered, ideally with a tight-fitting lid (such as a water bottle).  Uncovered water can become re-contaminated.

Note:  Water safety is almost never 100% guaranteed.  It’s one of those “most likely this will be fine” acceptability rates.  This is not meant to scare you, simply to make you aware of the situation.

Photo credit: brook peterson