Guest Post: How to purify water: 14 methods for homes and outdoors

This comes from the good folks over at RO Systems and details methods for purifying water- a critical skill to know to maintain your own health in any environment. Dysentery sucks. -NCS

Knowing how to purify water at home and in the outdoors is an essential survival skill. The human body can live for over a month without food, but can only last three to four days without water.

One of the first and primary skills survival experts focus on is how to get access to safe, clean, and drinkable water. Water is so essential that it is important to know how to make water safe and drinkable.

If you live in the United States and you get your water from the city, it is mostly safe to drink. If you have a personal well, it would depend on the location and how deep the well is. When in doubt, you should contact your local authorities for location-specific information.

How to purify water: 14 methods

The following lists many ways to purify water. Each method has its own advantages and disadvantages, and depending on the need, how much prep time you have, and access to materials will determine which method is best for you.

However, no matter what method you use, you will also want to know how other water purification systems work.

1. Boiling

Boiling water is just what is sounds like. You take a pot, fill it with water, add heat until the water boils, and once the water cools it should be safe for drinking. This is a common method for sources of water that may be contaminated with pathogens, bacteria, and other unsafe organisms.

How it works

Boing water kills unsafe pathogens, bacteria, and other unsafe microscopic organisms that may be living in the water. In areas where the water is known to be infected with these harmful microscopic life, it is important at the very least to boil your water.

What does it remove?

Boiling the water kills harmful microscopic organisms that can make people sick if consumed.

How to do it

Boiling water is extremely easy. Some people boil their water just to be safe, even if there is no known pathogens or bacteria issues with the water. You will need a pot to hold the water, and a heat source like a stove. Simply fill the pot with water, and then heat the pot until the water is at a rolling boil. Once the water has cooled again, it is now safe drink.

Advantages and disadvantages

Some of the advantages is that this is super easy to do. Anybody can boil their water if there is a concern that it may be contaminated with harmful microscopic organisms. It requires no special equipment, and everyone should have some way to boil water.

Some of the disadvantages is that people who drink boiled water often complain that the water has a metallic taste. Also, this method only deals with eliminating pathogens, bacteria, and other harmful forms of microscopic organisms.

It will not remove any other pollutants that may be in the water such as mud, chemicals, or other harmful materials. It only kills the potentially harmful microscopic organisms.

2. Iodine

Iodine is another method that has been around for a long time to purify water. Using iodine may not have been around as long as boiling water, but it is still a proven method for purifying water quickly and reliably.

How it works

Iodine either comes in tablets that will dissolve in water or in drops. Iodine is the favored method for purifying water in outdoor wilderness survival type settings.

It works similar to boiling water by being very effective at killing harmful pathogens, bacteria, and other microscopic organisms in the water.

What does it remove

Iodine has been proven to be quite effective at killing pathogens, bacteria, and other microscopic organisms from the water. It does not remove other pollutants, chemicals, and other harmful substances in the water.

How to do it

To purify water using iodine, simply dissolve an iodine tablet into water, or put a few drops into the water depending on how your iodine is packaged. There are instructions on how much water should be used per drop or tablet, and should be on the container that your iodine comes in.

Advantages and disadvantages

Using iodine is quicker and easier than boiling water. So in a wilderness situation there is no need to create a fire or use a propane stove, all you need to do is combine the water and the iodine, and the water should now be safe to drink from pathogens, bacteria, and other harmful microscopic organisms.

This is the preferred method of backcountry hikers, who have access to natural sources of water that are free from pollutants, but may still have some harmful microscopic organism living in the water. Iodine is small and easy to carry, and very quickly the water is safe to drink.

Iodine will not remove any other pollutants from the water. So it is important to have a source of water that is pollutant free, and just needs to be treated for harmful microscopic organisms.

Also iodine can be toxic if taken in large amounts, and some people have an iodine allergy. If someone has an iodine allergy, is pregnant, or has a thyroid issue, then iodine should not be used to purify their water.

Also, it can discolor and change the taste of the water. Many find this unpleasant enough, to discourage use of iodine to purify their water.

3. Chlorine

Chlorine plays a major role in most modern water purification systems for cities and other municipal water sources. It has become essential to treat most municipal water systems, and may be used in a survival situation carefully when a source of water may have become compromised.

How it works

Chlorine is an efficient choice to kill harmful microorganisms that could be living in the water. It if effective enough for large scale use, and may even be used in survival situations.

Chlorine works by killing the harmful pathogens, bacteria, and other microscopic organisms that can be living in the water.

What does it remove

While it kills deadly microscopic organisms that may be contaminating the water, it does not remove any particles or other pollutants.

So using chlorine to purify the water may need to be treated also to remove any other pollutants that would still render the water unsafe to drink.

How to do it

If the water cannot be boiled, and there is no access to iodine, then regular household bleach can be used to make water safe to drink from harmful microscopic organisms.

However this must be done with great care because too much can be harmful. Using unscented laundry detergent, or unscented bleach is the yields the best results. It takes about 8 drops of bleach per five gallons of water.

Advantages and disadvantages

The advantages of this method are that it will definitely kill all of the pathogens, bacteria, and other microscopic life that could be harmful if consumed.

If mixed properly and in the right amounts it also does not significantly alter the taste of the water. Most cities use chlorine in their municipal water systems, because it does not change the look of the water, and does not alter the taste of the water. Because of this, cities use chlorine with some type of filtration system to take care of their cities water.

The biggest disadvantages to using chlorine long term to purify your source of water is that there may be some long term health effects of consuming to much chlorine.

This is an emerging area of research, but some experts warn that chlorine in the water could be leading to some serious health concerns. Also, chlorine does nothing to filter out other pollutants in the water.

4. RO machines

Reverse Osmosis (RO) machines used a water pump, and a semi permeable membrane to rid the water of pollutants.

How it works

Reverse osmosis machines are whole-house, under-counter, or countertop appliances. It is not a passive system, but uses a pump to build up water pressure to force the water across a semi permeable membrane.

This removes many of the microscopic organisms that are in the water as well as many pollutants that are in the water.

What does it remove

It removes from the water most of the pathogens, bacteria, and other harmful organisms in the water. While it does not kill these microscopic organism, it may remove some of a certain size (depending on the type of filter). It also removes many of the pollutants that are in the water as well, such as fluoride, chlorine, sediments, salt, pollutants, herbicides, and pesticides.

How to do it

Using a water pump the machine pumps the water across a semi permeable membrane. As the water if forced across this membrane it leaves behind various pollutants. Some of these machines can take out some microscopic organisms if they are large enough, however most machines do not.

Advantages and disadvantages

If you are getting your water from some type of city municipal water system, then it should already be treated for harmful microscopic organisms. This system will then take out other unwanted contaminants such as sediments, chlorine, and fluoride.

While this works great if you live in a city or there is another water purification system that is already at work, this is not enough to be the sole means of purifying water.

It needs to be used in conjunction with another system that will clean out the harmful microscopic organisms. Also it needs a reliable source of electricity to work, which may not readily be available in a survival situation.

5. Gravity filters

A gravity filter uses gravity to pull water through a filter which is used to purify the water. The process can be time consuming, and the materials may be somewhat expensive.

Also, this is possible as a DIY project, and many people in long term survival like situations will use some type of gravity filter for their long term water needs.

How it works

A gravity filter simply uses gravity to pull water through a filter. This is a passive yet time consuming activity when done correctly should yield perfectly good drinking water.

The concept of a gravity filter is similar to how the earth purifies water over time. In nature as water sinks through layers of soil, rocks, and other substrate, the water is slowly cleaned.

When the water eventually emerges in a natural artesian spring it is pure, and generally safe to drink without being treated further.

What does it remove

A gravity filter will remove pollutants and all types of particulate matter. If constructed properly it should also be able to remove many bacteria and some microscopic organisms.

How to do it

You can buy portable gravity filtration systems, that require no power. This is ideal in any survival situation, or for living off the grid. If you are in a situation where you need to create your own gravity filter, then you can create your own relatively easily. You would need at least two containers, one on top of each other.

The bottom container catches the water once it has gone through your gravity filter. The top container should feed into the bottom container, and this should have all of your layers that your water that should pass through.

It should have a mix of layers such as charcoal and stones, this will be the filters that the water will slowly pass through.

This takes a little bit of trial and error at first to get right, but you can also consult the internet where many people have, put up detailed plans for free. Also, many reputable vendors sell high quality gravity filters.

Advantages and disadvantages

One of the greatest advantage of the gravity filter is that it can be built with relatively inexpensive materials, and is the most natural way to purify water. Also, there are some great table top gravity filters that are available for sale online.

The gravity filter requires no power, and as long as you have time, then it is an extremely efficient water purification system.

The biggest disadvantage is that it will remove most but not all potentially harmful organisms. Also, the homemade versions tend to be fairly large and are not easily portable.

The ones that are available for sale has changeable filters that tend to be expensive, and the filters need to be replaced regularly to remain effective.

6. Make a DIY filter

It is fun and easy to make your own water filter at home. You can use items that you most likely have lying around the house to make a water filter that will get a lot of dirt and other pollutants out of your drinking water.

How it works

This DIY filter is going to use gravity and some materials you most likely have already to make a filter. First you are going to gather a soda bottle, a coffee filter, some cotton balls, activated carbon (or charcoal), sand, and some small pebbles. Now even if you do not have these items at home they are readily available.

The activated carbon may be the hardest to find. However, you can either make your own with some charcoal (and other ingredients), or buy some at any local pet store.

What does it remove

This DIY filter should remove all the big stuff out of the water. It should clean out all of the dirt, sediment, and other large pollutants from the water.

It will not address harmful microscopic organisms or harmful chemicals that may be in the water. So if this is used to drink pond water for instance, then this should still be boiled first to kill all of the harmful microorganisms.

How to do it

Cut off the bottom of the soda bottle and turn it upside down. Open the soda bottle and but the coffee filter over the nozzle of the bottle to keep everything in the bottle and to have a bit of extra filtration.

Then create a layer with the cotton balls, a layer of activated carbon, a layer of sand, and a layer of small pebbles. Once all your layers are in place, the filter is ready to be used.

Since the bottle is upside down it should be hung and allowed to drain into a bucket or bowl.

Advantages and disadvantages

The greatest advantage to this method is that anyone can do this. It is a cheap and easy filter than anyone can make with a little bit of work, and a quick trip to the store. This is a great DIY project if a situation arises that calls for being able to purify water at home.

The biggest disadvantage to this is that is a painfully slow method of filtration, and the water will still need to be boiled or treated to deal with potential microorganisms that could be harmful. However this is an effective water filter, and it is a great DIY project to learn more about how water filtration works.

7. Pitcher filters

A pitcher filter uses some type of ceramic or carbon filtration system that is inside of a water pitcher. This is probably the most common type of water filter. They are a convenient and relatively quick way to enjoy good quality filtered water.

How it works

A pitcher filter works by using a filter element that is embedded into the top of the filter. Water is poured into the top of the pitcher where it is then passed through a filter to the bottom of the pitcher.

After the water is gone from the filter section, then the pitcher is ready to use. The filter element is typically made of activated carbon and works through absorption, and the filter must be replaced every few months or so.

What does it remove

This will remove large sediments and pollutants. It will normally not remove any type of microscopic organisms. However if there is a heavy water issue such as lead, copper, or mercury in the water then this is a great solution to remove large pollutants from the water.

How to do it

A pitcher filter needs to be bought from a store or other online vendor. It is similar to a gravity filter as it uses gravity to pull the water though its filter, but it will not filter as many things out of the water as a good gravity filter.

Advantages and disadvantages

In terms of convenience the pitcher filter is one of the best options. The pitcher filter if very popular, especially for people in cities who have access to municipal water that have been treated for microbes, but want to remove things that municipal water systems do not deal with such as certain metals, chlorine, fluoride, or other materials that could be in the water.

8. UV light

UV Light purifies water that may be unsafe because of microscopic organisms using ultraviolet light. This is a water filtration system that does not deal with pollutants, but deals exclusively with microorganism.

How it works

It uses ultra violet light that is harmful to microorganisms that may be in the water. It scrambles the microorganisms DNA so that they are no longer able to reproduce.

The biggest danger in drinking water contaminated with microorganisms is that when many of them find their way into a person’s digestive track they settle down and begin to reproduce.

This can lead to a person drinking the water infested with these microbes to become sick or even seriously ill. The ultra violet light renders the organisms unable to reproduce, and they will simply pass through your system.

What does it remove

It does not truly remove anything. Instead it sterilizes the microorganisms that could be in the water, so that they cannot reproduce inside of a person and make them sick.

How to do it

This is not a do it yourself type of project. This is something that is going to need to be bought from a retailer that specializes in producing ultra violet light to treat the water for microorganisms.

Advantages and disadvantages

While if you already have access to water that is free from pollutants, and only need to deal with a microorganism contamination issue, then this is a great solution. It does not take a lot of power, and it leaves in some health microbes that are actually healthy for the human body to consume.

The main disadvantage is that it is not actually taking anything out of the water, or adding anything that could be helpful. This needs to be paired with some other type of water filtration system that will take out all of the other pollutants in the water.

9. DIY solar distillation (evaporation trap)

Knowing how to use solar distillation to create your own evaporation trap can be crucial in a life or death survival situation. The evaporation trap, uses a process that takes place naturally on earth, that naturally filters water of both pollutants and microbes. It can be made with a variety of materials that could easily be available in a survival situation.

How it works

It works by using evaporation to naturally separate water form contaminants, pollutants, and microbes. It uses the sun to heat the water and cause it to boil off as steam. Then a collector is used to collect the pure clean water, while the contaminants tend to rest on the sides of the evaporation trap.

What does it remove

An evaporation trap will remove both microbes and pollutants is used correctly. A evaporation trap does not make a lot of water, but in a survival situation even a little bit of water can make the difference between life and death.

How to do it

While you can buy a solar distillation (evaporation trap) commercially as a survival kit that you can take with you for emergency situations, an evaporation trap is something that you can easily make on your own from materials readily on hand.

This can be made by digging a hole and using a tarp, or using some water bottles duct tapped together. There are a lot of great DIY evaporation trap projects online.

Advantages and disadvantages

The main advantage is that with a little bit of knowledge, and some very common materials there should always be access to reliable water no matter what conditions are going on.

While this is not the easiest way to get purified water, with a bit of practice this can be a reliable source of water in even the harshest conditions.

10. Survival straws

A survival stray is a device that can used to drink water from almost any source. It is often used by those who engage in outdoor wilderness activities who may be far from more reliable sources of water. It is a great tool to be a part of any survival kit, and can mean the difference between life and death in survival situations.

How it works

The survival straw works through suction. When a person sucks on the straw it draws the water up through a microfiber filtration device that removes contaminants. This is a powerful tool that uses a natural suction power to filter a source of water, and makes it safe for its user to drink.

What does it remove

The survival straw removes bacteria, parasites, and microplastics. It does not remove salt and other dissolvable substances that may be in the water.

How to do it

The survival straw is not a DIY project and should be purchased from a reputable vendor. These durable and lightweight survival tools last a long time, and most are good for slurping up over 1,000 gallons of water before needing to be replaced.

Advantages and disadvantages

The main advantage of this product is that it is extremely portable, and can easily be packed to be used in any type of survival situation. It may not be able to purify salty water, but in a pinch it can be used to safely drink many natural put unsafe sources of water that may be encountered.

The main disadvantage is that you will need to pack this beforehand. This is not something you can build on your own, and will need to be purchased in advance.

Also, the survival straw is useless for taking out substances that fully dissolve in water such as salt. It will not be good for purifying ocean water, or recycling urine.

11. SODIS(solar water disinfection)

Solar water disinfection developed in the 1980’s to be an inexpensive solution to purifying water. It uses a clear plastic bottle and the sun to purify water from potentially harmful micro biological organisms.

How it works

The procedure is relatively straight forward and easy to execute. Simply fill a plastic bottle or other container with the water you wish to purify. Close the bottle then give it a good shake to oxygenate the water, and then place the bottle out in the sun. Leave the bottle out for around six hours on a sunny day, and up to 2 days if it is cloudy.

The ultra violet light from the sun, and heating up the water should make the water safe from dangerous microbes that may be in the water.

What does it remove

The process of solar disinfection should damage any microscopic organisms that are in the water, and render the hazardous microbes harmless. They will still be in the water, but they will no longer be able to cause disease by reproducing in the body.

How to do it

Solar disinfection is an easy process to do, and can be done with items that should be readily on hand. In a survival situation keeping a plastic bottle on hand can come in handy.

If there is a water source that needs to be made safe for drinking, then it is easy enough to do use solar disinfection as long as a bottle is handy and the sun is cooperating.

This has also been used in developing nations as a means to disinfect large quantities of water for drinking, to help stop the spreading of infectious diseases from pathogens, bacteria, and other microbes in the drinking water.

Advantages and disadvantages

The biggest advantage of this method is that it can be used to make a lot of water, and to make it relatively passively. You are only limited by the amount of clear plastic bottles you can find, and by the amount of sunlight you have during the day.

Once you set up the solar disinfection system, it frees you up for at least 6 hours or so to do other tasks. Also, in many countries where there are no reliable water treatment services this method has literally saved thousands of lives.

Perhaps the biggest drawback to this method is if there are other concerns with the water besides microorganisms. If there are other pollutants in the water such as loose sediments, fluoride, chlorine, fertilizers, herbicides, or other chemicals, then this method will not clear them out of the water.

The water will have to be filters by some other means as well to get those pollutants out. Also, it does take about two days when the weather is cloudy, so it is not the most efficient method for purifying water.

12. Ozonation

Ozonation is a process by which ozone is added to water by a ozonation machine. Ozone, also known as molecular oxygen, is the most stable form of oxygen, with oxygen being chemically bonded to itself. Ozone has a lot of purported health benefits.

How it works

Ozone is added to water by treating the water in a machine that is designed to add ozone to the water through a process of electrical discharge.

This process would happen naturally in the environment by a high electrical discharge such as a lightening strike. However, an ozonation machine can be used to create this type of water.

What does it remove

This process can be used to add a negative charge to the water, which may have some health benefits, and it is also very useful at dealing with harmful microorganism without adding harmful chemicals.

How to do it

You can purchase a ozonation machine for home use. This is a system that needs to be plugged in to be used, and so in a survival situation it will not be of much use. However, many people have a countertop machine at home, and enjoy this water very much.

Advantages and disadvantages

The biggest advantage to this method is treating the water for dangerous microorganisms without having to use harmful chemicals, boiling the water, or other methods to deal with the potential dangerous microorganisms.

Also, many enjoy the taste of this type of treated water, and there may be some great health benefits as well.

The biggest drawback to this method of course is that it is a fairly large appliance that needs to be plugged in to do its job. This can be a real setback in a survival situation, but it should be fine for regular home use.

13. Purifying with plants

It is a little known fact that certain plants can be used to make water safe to drink from potentially harmful microorganisms.

How it works

Purifying water with plants works by soaking the plants in the water. This releases naturally occurring antimicrobial substances into the water, that kill the harmful microorganisms. This will make your water safe to drink form harmful microorganisms.

What does it remove

This method will deal with harmful pathogens, bacteria, and other microscopic organisms. However it will not deal with dirt, sediments, or other pollutants in the water.

How to do it

There are a variety of plants that will purify water when soaked and these include:

• Banana Peels
• Fruit Peels
• Jackfruit Seeds
• Reeds
• Bulrushes
• Rice
• Coconuts
• Java Plum Seed
• Moringa Oleifera
• Oregon Grape
• Other Citrus Fruits

Advantages and disadvantages

The biggest advantage to this method is that it naturally deals with harmful microorganisms in the water, and often adds a nice flavor to the water.

This takes extensive knowledge of local plants, or access to these from a local grocery store. However, it is a great way to add flavor and improve the quality of your water, especially for at home use.

The biggest disadvantage to this technique is that in a survival situation a vast knowledge of identifying wild plants is needed. Identifying plants in the wild is not east.

Also, many of these plants are specific to certain geographic locations, so unless you are in the right place, at the right time, then this may not help much.

14. Sedimentation

Sedimentation is a physical water treatment process that uses gravity to remove pollutants such as rocks, dirt, and other large solids form water.

How it works

This process takes place sedimentation tanks or basins. As dirty water if brought into the basins it is moved through the tank with a steady current. As the water passes through the sedimentation tank large solids settles to the bottom of the tank.

As the water moves out to the sedimentation tank it leaves these large pollutants at the bottom of the tank, and the cleaned water is now ready for further treatment and filtration. This is usually one of the first steps in a large municipal water treatment procedure.

What does it remove

It removes large pollutants such as dirt, rocks, and other large solids from the water. However the water is still not fit to drink, and must be further processed for both harmful microorganisms, and further filtered for other solids that may still be in the water.

How to do it

This process takes advantage of a physical property where sediments in water tend to sink to the bottom of a tank. This allows the a layer of sediment (or muck) at the bottom of the tank to be separated from the partially cleaned water near the top of the tank.

This is accomplished through a mechanical device actually scraping away the muck at the bottom of the tank, and the cleaner water flowing out of the tank. After the water passes through several of these types of tanks it should be ready for further processing.

Advantages and disadvantages

The biggest advantage of this method is that it takes advantage of the physical properties of sediments in waters tendency to sink to the bottom.

Once this system is set up, it can go a long time without further maintenance, and makes it easier for further filtration and dealing with any harmful microbes that may be in the water.

The biggest drawback to this method is that it takes large tanks to make this practical, and the water is still not considered safe to drink after going through sedimentation, and will still need further processing.

Conclusion

Learning how to make water safe is an important survival skill. Whether you are at home or outdoors it is vital to understand how to purify any source of water.