7 Ways to Purify Water for Urban Survival That Actually Work

When the situation turns truly grim, the liquid stuff that flows so freely now from your taps might be exceedingly hard to find, and what you manage to rustle up might be beyond contaminated. What can you realistically do in this scenario?

There are various effective ways to purify water for safe drinking in urban survival situations. We may classify them under mechanical filtration, heat treatments, chemical treatments, and UV light treatment. These are all methods you can implement as an individual during emergencies. 

We’ll be getting into the world of water purification in all its various forms here today. You will find all you need to know about each method’s effectiveness, convenience, appropriate scenario, and more. With a bit of knowledge, foresight, and preparation, we can avoid some of the more severe privations and consequences of a truly mucked up situation.

Why We Need to Purify Our Drinking Water

The last thing you want while trying to keep body and soul together in a survival situation is for you or a loved one to fall ill due to drinking contaminated water. Dehydration will be the hard place behind us as we face the rock of possible water poisoning. Effective water location and purification will be the safest way out of your dilemma.

Without meaning to be pessimistic, the reality has to be acknowledged that urban water stress might occur for many reasons, be they man-made or natural. Chemical contamination, biological contamination, power grid outages, and nuclear contamination are some of the possibilities that may result in severe potable (drinkable) water shortages.

The ravages of Hurricane Katrina, the Flint, Michigan water crisis, and the regrettable outcomes of the Toledo water contamination crisis immediately come to mind as examples in recent memory. You don’t have to be in some type of desert to go without safe drinking water. Waterborne diseases such as dysentery, typhoid, cholera, and more are real dangers when dealing with untreated water.

There are plenty of potential dangers that might be lurking in whatever water you are able to find somehow, including protozoa (Cryptosporidium, Giardia, etc.), bacteria (Salmonella, E. Coli, Shigella, Campylobacter, etc.), viruses (Rotavirus, Norovirus, Enteric, Hepatitis A, etc.), various harmful chemicals, and a variety of toxins.

Even with what seems like adequate water stockpiles in place, one never knows how long they’ll have to rough it before things get back to normal – if they ever will, that is.

The result is that in due time, alternative water sources will have to be called into service. Streams, ponds filled with algae, muddy puddles, water fountains, swimming pools, ocean water, rainwater, and other more ‘creative’ resources might have to be dipped into to furnish this precious commodity.

The exact method or methods you decide to use for your purification purposes will depend on the scenario in question, what you have available, and the condition of whatever water you’re able to find. There really isn’t one ‘best’ method when it comes to water purification.

Rule of 3s

The Survival Rule of 3’s states that people will only survive 3 minutes without air, 3 hours without shelter, 3 days without water, and 3 weeks without food. Whether that makes some sense to you or not, it does give us a good basic checklist for emergency survival planning and prioritization.

It might be all too easy to discount the importance of clean running water when it’s in plenty, but you definitely do not want to be caught completely unprepared should the brown happen to hit the fan. 

As they say, being informed is half the battle won. With that in mind, it will be useful to have the following list laid out as it relates to effective water purification methods. It should include details regarding what they will protect you against, the best scenarios for their use, and any downsides they might have.


Boiling water will effectively eliminate many different contaminants, especially biological ones, including viruses, protozoa, parasites, and bacteria. Still, it will do little to protect you from organic chemicals, inorganic chemicals, and radionuclides.

Understandably, most people do not consider radionuclides or radiation contamination to be a realistically clear and present danger, even in their wildest imaginings. However, it should be a real consideration for those living close to nuclear power generation facilities. You might also want to keep it in mind whenever you feel World War III is about ready to kick off (always?).

Anyway, the Red Cross advises that to ensure our drinking water is free from the microorganisms mentioned above, we need to heat water until it comes to a boil and leave it boiling for one minute, at least. We may then allow it cool and then drink it. Filter the water through a piece of cloth if you spot some deposits in it or let it decant if you really don’t have a makeshift filter close to hand.

Boiling is a solid and reliable water purification choice due to its relative ease and simplicity. Most of the time, all you will need is some time on your hands, a clean pot, and a source of heat. Even if you can’t rely on your stovetop here because the power is out, you can always chop up that cabinet you never liked for firewood.


This is the heating water process so that it converts to steam, collecting the steam and letting it cool down in a separate vessel to give you potable water. The idea behind it is that the harmful microorganisms, debris, and pollutants will be killed, denatured, or left behind in the first container.

While distillation is great at getting rid of most potential threats such as parasites, bacteria, protozoa, viruses, inorganic chemicals, and some radionuclides, most setups will not work effectively against certain organic chemicals. Such chemicals may include pesticides and other volatile organic compounds (VOCs), which will become vapor quite easily, meaning they will remain present in your distilled water.

There are great water distillation units such as the Megahome Countertop Water Distiller, which operates at 212 degrees Fahrenheit for optimal microorganism elimination, can distill up to 5.5 gallons of water per hour, and includes modular activated charcoal filters which will take care of the VOCs many other distiller models cannot. It works great for saltwater as well.

Distillation will be a suitable purification method when handling tap water in times of power outages (if you have a backup generator) and when dealing with floodwater, nuclear disaster situations, or backcountry water. It will be an especially vital survival prep bit of equipment for those living near the ocean. It is perhaps the best method of eliminating salt from ocean water efficiently for safe drinking.

Take note that water distillation with commercial setups will require a source of electricity to work and may take some time to accomplish, meaning blackout scenarios will call for standby generators.

Ultraviolet Light Treatment

Ultraviolet lamps (UV lamps) can be effectively made use of to make questionable water potable. It does interfere with the biological functions of organic contaminants in the water, rendering them inert and harmless. However, some organisms such as Cryptosporidium and Giardia will be killed completely by this process.

When microbes are exposed to UV lamp radiation, it induces slight changes in their DNA structures, which inhibit their reproduction. Viruses require prolonged exposure to germicidal UV light to experience DNA unraveling and consequent death.

Should the water in question be visibly cloudy due to impurities or debris suspended in it, the best course of action will be to run it through a filter of some sort or decant it first. When the water is too cloudy, harmful microorganisms in it may be shielded from your UV lamp’s effects, rendering your purification efforts moot.

The germicidal or microbe-killing wavelengths of UV light are on the shorter side, ranging from 100 to 280 nanometers (nm). This is the range at which most UV lamps operate to maximize their effectiveness. In contrast, visible sunlight falls within the 330 to 500 nm range. 

You can get your hands on an effective UV wand such as the SteriPEN Ultra UV Water Purifier that will effectively take care of 99 percent of harmful waterborne microbes, is easily rechargeable via USB, and will purify over 3,000 gallons (over 13,000 liters) of water in the course of its working life.

You should also note that water that has been treated with this method should not be left to stand in direct sunlight (visible light) for any significant length of time afterward. The danger here is that this type of light has the capacity to reactivate the inert microbes still in the water through a process known as photoreactivation, making it unsafe to drink once again. Drink the water as soon as possible or store it in a dark place.

So we see that the portability and effectiveness of UV light treatment make it a great solution for urban survival situations. The fact that it works very quickly makes it even more suitable here. You won’t have to worry about bacteria, parasites, viruses, and protozoa, although organic chemicals, inorganic chemicals, and radionuclides will not be effectively taken care of. Batteries or a charging power source will eventually be needed as well.

Chemical Treatment

This refers to water purification methods that rely on introducing certain chemicals into the water to kill or neutralize whatever harmful microbes it may contain. While various chemicals are capable of doing this job, the most effective and widely available ones are iodine, sodium chlorite/chlorine dioxide, and potassium permanganate.

Note: The chemical purification methods work best when applied to pre-filtered, non-cloudy, settled water at around normal room temperature.

Iodine for Water Purification

Iodine tablets, tinctures, and crystals are widely available for water purification purposes, and they are very popular due to their portability, ease of use, and the impressive quantities of water that may be treated with a bit of iodine (a small container of iodine crystals can treat more than 10,000 gallons of water).

If you’ve got iodine tincture (concentrated iodine in liquid form), you will mix in about 30 drops of it per gallon of water.

In the right amounts, it is actually necessary for proper thyroid function and good health for humans. This is the reason the United States government mandated its inclusion in table salt back in the 1920s. Even so, in excessive amounts, its effects become toxic.

When using iodine for water purification, it is vitally important that you do not exceed the recommended iodine-water ratio. You should also avoid using it for more than a few weeks at a time due to the risk of accumulated buildup in your system.

Pregnant women, iodine-allergic people, and those with thyroid problems should not drink iodine treated water. While many people dislike iodine’s smell and taste, it is far from overpowering when mixed in the correct proportions.

Sodium Chlorite/Chlorine Dioxide (Bleach) for Water Purification

This treatment method makes use of chlorine and its compounds to purify water through the process of chlorination. Water chlorination is the method used by municipalities worldwide to treat the water that comes out of your taps. It’s favored because of its effectiveness and high safety rating for human consumption.

While chlorine works by fatally destroying bacteria and other microbes’ cell walls, it is innocuous when ingested by human beings because it will very quickly be neutralized within our digestive systems. 

Swimming pools are regularly treated with higher chlorine concentrations, yet young and old can swim in them without harm, even should they swallow plenty of the treated water. 

Still, pools can have too much chlorine in them, which may react with human waste products such as caveat and urine to form chloramines, affecting the skin, eyes, and nasal passage of the swimmers.

Now, the chlorine you will want for urban survival preparation is the type that comes in tablet form. Each tab has the capacity to treat one quart of water, and the foil packaging makes it a very easily portable, convenient resource for any bug-out kit as well. Drop the tab in your water, allow it to sit for some time, and your water will be safe to drink.

Should you find yourself without chlorine tablets at hand, there is a household solution you can make use of instead. Common household bleach can perform the work of chlorination just as effectively, but be sure that it is unscented, has no additional cleaning agents mixed into it, and states on its label that it is not color safe (contains 8.5% sodium hypochlorite).

Mix in 6 drops of this type of bleach for each gallon of water intended for the treatment and allow it to settle for at least 30 minutes before drinking. Chlorination either with tablets or household bleach is a cheap and readily available purification method that will eliminate parasites, bacteria, protozoa, and viruses but will not effectively deal with organic chemicals, inorganic chemicals, and radionuclides.

Mechanical Filtration

Mechanical filtration refers to the method by which the common water filters most are familiar with function. The fact that they physically separate the impurities in the water from the water itself, without any chemical or biological processes involved, is what merits them the term ‘mechanical.’

Now, there is a broad spectrum involved when speaking of water filters, which makes it important that you put plenty of consideration behind your filter choice. The most important factor to consider will be the micron size rating of the filter in question.

This rating denotes the size of your filter’s pores and determines the size of particulates it will be able to screen out of your water and what it will allow to pass through. The general rule here is that the smaller the micron rating, the more effective and comprehensive it will remove pollutants and contaminants.

Here’s how the ranking goes:

  • Simple filtration: This might include filtering your water through a finely woven cloth material such as silk will eliminate a significant amount of polluting material, but this will only help make the water clearer without taking care of any microbes. This type of filtration is nonetheless a good step to take before further purification measures.
  • Microfiltration: This takes things a step further as it involves filters with a rating of 0.1 microns. This will effectively filter out protozoa and bacteria in your water but will not do much when it comes to viruses or chemical elements present.
  • Ultrafiltration: This is the gold standard of mechanical filtration and is what you should be aiming for when contemplating drinking water purification. Ultra-filtration filters are those with a pore size of 0.02 microns at most, which will definitely eliminate protozoa and bacteria as well as provide protection against viruses and inorganic chemical contaminants.
  • Nanofiltration: This goes even further than microfiltration but doesn’t feature much infiltration systems that can be used at home, much less carried around in your bug-out kit. It involves a process known as membrane filtration used in industrial or commercial settings dealing with pharmaceutical products, bulk chemistry, petroleum chemistry, and such. Membrane pore sizes can be as small as 0.001 microns, which is 1 nanometer.

So we see that while filters may come in a wide variety of cheap and highly portable options, most of them will call for additional purification measures such as boiling to neutralize any potential dangers completely. Most models will effectively take care of parasites, bacteria, protozoa, and inorganic chemicals but will do little to eliminate viruses, organic chemicals, and radionuclides.  

These filters fall into the microfilter category, with a good example being the MSR MiniWorks EX Microfilter. It filters at the rate of 1 liter per minute, with each of its replaceable carbon cartridges being good for processing 2,000 liters before needing changing.

For a larger household option, we use and recommend a Royal Berkey gravity-fed water filter. We have been using one for years and can’t say enough good things about it.

Activated Carbon Filtration

Activated carbon can also be referred to as activated charcoal, with the ‘activated’ part simply meaning that it has been ground down to make a fine powder. This is to increase the surface area available for contaminants’ adsorption, which is how it works to help make our water more suited to drinking.

What makes activated carbon special is that it is perhaps the only accessible water treatment material that will eliminate organic chemicals and some low-quantity radionuclides. Should you have your home located in the vicinity of a nuclear power station, chemical or industrial plant, or in an area where commercial agriculture occurs, this should definitely be part of your emergency preps.

To be clear, activated carbon filtration will not eliminate common threats found in your water, such as bacteria, viruses, parasites, protozoa, and inorganic chemicals, which is why it should not be used as a standalone measure.

For example, should you be concerned about contamination when forced to use flood water for your drinking purposes, you can boil the water first to eliminate the usual threats. Then run it through your activated carbon filter to catch any toxic organic chemicals (pesticides, benzene, etc.) that may have leached into the water that boiling or other purification methods will not. 

Note that activated carbon filters cannot be used indefinitely. In fact, they should be changed out regularly. The reason for this is that carbon filters will get saturated relatively quickly, especially if the water is heavily contaminated, meaning that past a certain point, they will no longer be working as they should. The problem is exacerbated because it isn’t easy to tell when this point has been reached.

Therefore, we feel that carbon filtration makes for a useful addition to any emergency kit. It can come in handy during flooding, industrial site incidents, biochemical attack scenarios, and low-level fallout from nuclear attack, manmade, or natural incidents.

You can, as a matter of fact, use it for more than water filtration. Its toxin-absorbing qualities make it a useful resource in cases where poisoning is suspected. This includes alcohol poisoning. Simply ingesting some activated carbon can help reduce alcohol and toxin levels in a person’s bloodstream.

Note that it should NOT be given to children less than 1-year-old. Disclaimer…this is food for thought and you should reference professional medical advice before trying.

Reverse Osmosis

While the threat of nuclear fallout radiation due to attack or perhaps due to an accident such as what occurred in Fukushima or the famous Chernobyl may seem like a far-out possibility, being prepared means expecting the unexpected.

That’s why this list wouldn’t be complete without mentioning reverse osmosis filtration. It works by applying pressure to water against a semi-permeable membrane that will not allow molecules above a certain size to pass through. Here, water molecules are allowed through, leaving any impurities and contaminants behind.

It ranks as the most effective water purification system short of industrial or commercial units, as it is highly effective in eliminating any bacteria, protozoa, parasites, viruses, inorganic chemicals, and radioactive materials that may be present in your water.

Why doesn’t everyone go for reverse osmosis units, then? You might be asking yourself. Well, they are relatively expensive, for one, let alone that they are not portable and require running water (functioning water supply systems) to function. This last limitation might render them ineffectual in certain situations.

So who needs them if that’s the case? As we’ve seen, reverse osmosis systems are at the top of the list when it comes to water purification effectiveness. They will perform just as well as any of the other systems we’ve covered here, if not better. For those who can spare the cash, they make for a useful home addition that will serve you in normal day-to-day life as well.

The people who should strongly consider making the extra effort to get their hands on one of these systems are those living in the vicinity of nuclear facilities – or Washington, D.C., if we can trust Hollywood to know anything about it. This will be your surest bet against radioactive material contamination in your water supply.

It will take care of photon and beta particle radiation, alpha emitters, uranium, radium 226, radium 228, cesium, and more in addition to the usual bacteria, parasites, viruses, protozoa, and inorganic chemicals. 

It only falls short when it comes to organic chemicals, that’s why a system that combines reverse osmosis technology with activated carbon filtration such as the Water Drop Reverse Osmosis Water Filtration System is a near foolproof setup to have in your home.

Final Thoughts

Take the time to explore and become knowledgeable with regards to the water situation in your surrounding area so that you have a good idea of potential emergency water resources. This is important as even the largest reserves won’t last you forever.

In urban survival conditions, the unavailability of safe drinking water might become a real threat to your health and safety much sooner than you’ll have to worry about running low on other resources.

While it is always wise to have emergency water reserves in stock, it may not always be feasible in urban settings. Having a reliable method of ensuring whatever water resources you manage to acquire will see you have safe, potable water for a long time.

Cody Martin

With over 18 years of federal law enforcement, training, and physical security experience, Cody focuses his time nowadays on both consulting and training. He regularly advises individuals, groups, multinational corporations, schools, houses of worship, and NGOs on security threats while conducting customized training as needed.

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