5 Methods for Purifying Water in Survival Situations – Survival Prepper

5 Methods for Purifying Water in Survival Situations

the Steri-Pen in use: one set of batteries purifies up to 40 gallons of water with UV radiation

The Steri-Pen in use: one set of batteries purifies up to 40 gallons of water with UV radiation

Disaster preparedness experts recommend you keep three days’ worth of clean, ready-to-drink water (5-6 pints) in your emergency supplies kit. Store-bought bottled water with an unbroken seal will last for years if stored in a dark, fairly cool spot. Refilling opened bottles is fine- you’ll just need to check on them a little more often, and maybe replace the water to make sure it still smells fresh and healthy.

In a disaster situation, that three days worth of water is supposed to last you the time it takes for the taps to come back on. But after a serious natural disaster, or if you have to leave town and head for the hills, you’ll need more than three days of drinking water, and you’ll also need clean water for cooking, washing food and equipment, and personal hygiene. It’s important to note that during a disaster you shouldn’t assume your tap water is safe: serious natural disasters (landslides, subsidence, volcanic activity, hurricanes, tsunamis and flooding, for example) as well as sabotage can both compromise the safety of your drinking water supply with harmful chemicals and disease.

With basic survival skills, plus a bit of plucky ingenuity, you’ll be able to use the tools at your disposal to turn any water source of dubious respectability into safe, clean drinking water.


5 different ways to purify water


Whether you are collecting rainwater from a dirty rooftop or freshwater from a river or lake, you should filter that water before purifying it. Filtration takes out the leaves, dirt, and other macro pollutants, as well as visible bugs. You can sieve brackish water with a plastic or metal pasta strainer (an old (clean) t-shirt will work as well), but to really get it looking, tasting and smelling like clean water, you’ve got to use a slow-drip gravity filter.

Before the SHTF, you can invest in premade gravity filters. Traditional ceramic urns have recently received a bit of a high tech upgrade and some renewed popularity, and replaceable cartridge filter jugs like those made by Brita are easy to find. If you prefer to drink filtered water anyway, you might as well stock up on the replaceable components of your filtration system: better to have them sitting in your ‘vault’ rather than on the department store shelf when SHTF.

You can chain filtration methods to get your water cleaner and to extend the life of precious filter cartridges: knock up a crude sieve plus a more advanced home-made charcoal filter and rig up a water container to drip feed through one filtration system into the next. These things are slow, so being able to run them without attention is worth strategizing towards.

Once you’ve filtered all the physical impurities out, it’s time to deal with the pathogens.


  1. BOIL IT

Your bug-out-bag should include three ways to start a fire as part of your core inventory. A small pot for boiling water is a good option, but you should be able to find a suitable pot if you don’t already have one on you.

How to effectively destroy germs by boiling:

The important thing is to bring the water up to a rolling, bubbling boil and keep it there for five whole minutes. Your electrical kettle doesn’t boil water for long enough to kill germs. Weirdly, if you’re in the mountains, you have to boil it even longer: add one extra minute per 1000 feet above sea level.

Find a lid that fits your pot nicely (or just ensure the one you buy/glean for your pack has a fitted lid). This will bring water to temp faster (conserving precious fuel sources), and prevent pure water from escaping in the form of steam.



Water purification tablets or liquid chemicals are a staple of bug out bags and field survival kits. The tablets are relatively cheap, very lightweight, and easy to store long term or carry around. The most popular active ingredients are iodine or chlorine, but there are others, all with various pros and cons such as shelf-life, taste, and price tag. These chemicals are all made to kill bacteria, and should be combined with a filtration method as well. Filtering after as well as before chemical purification may help to get rid of the dead bugs and the weird added chemical taste. To encourage children and the elderly to keep their fluids up if the water is otherwise unpalatable, you can try adding powdered water flavoring like tang or iced tea.



How to set up a DIY solar still

You’ll need:

  • A large bowl, preferably made from shiny metal;
  • A jar, mug or metal/glass/ceramic jug
  • A sheet of transparent plastic (I’ve used saran wrap)
  • Something to use as a weight
  • Something to hold down the edges of the plastic

In a humid area, you can dig a hole and trap moisture in the air. But let’s assume an urban environment, or a suburban backyard. This method will work just as well somewhere humid, and can be scaled really well. Experiment by mixing some mud or coffee into clean water and see what happens!

  • Place the bowl in sun, somewhere where it will get as much direct light throughout the day as possible
  • Fill the bowl with the water you want to purify
  • Place the jar etc. inside that water, in the center of the bowl, making sure to avoid impure water getting inside it.
  • Stretch your clear plastic over the entire rim of the bowl, and seal it as well as possible around the sides with elastic or tape or cord etc. Saran wrap does alright by itself but a breeze will interfere. The plastic needs to have enough ‘slack’ to dip down slightly toward the center, but not so much that it touches the jar. Usually it’s enough to stretch the plastic taught and then place a stone in the middle.
  • The heat of the sun causes water to heat up and evaporate over time, condensing on the underside of the sheet of plastic, where it will run down toward the lowest point and drip into your jar.
  • After the evaporation process, impurities stay behind, and clean water goes in the jar.
  • Note though that any water-borne pathogens that can also move through air can hop straight from the bowl into the jar: this is more a method for filtering non-pathogen pollution out of your water source.



Zzzzzzap – lasers! No, not quite.

A Steri-Pen is a water purifying device that concentrates UV light to literally radiate the life out of everything in your water. One of these will sterilize a quart of water in only 90 seconds. They need batteries, but one set of double-As will purify about 40 gallons of water, enough to last you three months.
UV purifiers offer a lot of utility: they’re easy to use in snow and high winds, fuel scarcity doesn’t matter (so long as you have batteries), and they don’t produce smoke (that could attract unwanted attention). You can hide the whole thing in a box while the light’s on, making it very stealthy indeed. Making a sand and/or charcoal filter takes time and materials that you won’t always find. A gravity filter cartridge/jug combo is relatively quick, stealthy, easy to use, and as easy to stockpile as Steri-Pens and AAs, but it won’t kill pathogens.