How to Filter and Purify Rainwater for Survival Use

In a survival situation, it is important to know how to filter and purify rainwater for safe drinking. This guide will teach you the basics of how to do that.

If you are in a survival situation where you have the means to collect fresh clean rainwater you are in luck because rainwater is for the most part already safe to drink and does not need filtering. There are exceptions to this rule, for example, if there have been large fires, volcanic activity or you are in an area of high pollution.

How to Filter and Purify Rainwater for Survival Use

Unfortunately, collecting fresh rainwater is usually not as simple as placing containers out to collect freshly fallen rain. In most survival situations the rainwater you will collect will be from rock pools, depressions in the land, or from a stream. In these cases, you will want to filter the rainwater to ensure it is safe to drink.

Collect Rainwater in a Clean Container

The first step is to collect rainwater in a clean container. such as a water bottle canteen, metal cup, or even a pot if you are lucky enough to have one. Ideally, the container you have is made from metal, because then you can use the container to boil the water directly.

After you’ve collected the rainwater, you need to boil it, ideally for five minutes on a rolling boil to ensure that all pathogens are destroyed. If your container is metal then this is an easy step just place the container over a fire.

Collect Rainwater in a Clean Container

Where it gets tricky is when you have a plastic or other non-metal container. But don’t worry you can still boil water in a plastic container, what you will want to do is heat some rocks in the fire, and using two sticks like chopsticks, place them into the container. Be careful not to drop the rock to the bottom of the plastic container, or it may melt the base.

Filter the Boiling Water Through a Coffee Filter, Cheesecloth

This step can usually be skipped as rainwater is usually already free from debris, but if you used the hot rock method there could be some dirt and ash contaminating the water, in this case, you may want to remove it.

After the rainwater has boiled, filter it through a coffee filter, cheesecloth, or clean cloth such as our shirt to remove any dirt or debris.

Allow the Filtered Water to Cool

Once the water has filtered, it must be allowed to cool before drinking. It is essential because you could scold yourself if you try to drink boiling water. If you have some tea bags you could of course just make a nice hot cup of tea instead.

Allow the Filtered Water to Cool

Keep Any Extra Water in a Covered Container

If you have any unused water, store it in a clean, covered container. It will keep the water from becoming contaminated.

Now that you know how to purify rainwater, you can be sure you’re safe when drinking from streams or other water sources. You can also use this knowledge to help others who might not know how to purify water correctly.

Use Charcoal and Sand as a Filter

It is possible to make a crude water filter using charcoal and sand. This will not remove all of the impurities from the water, but it will make the water much safer to drink.

We have a full guide on how to use charcoal, gravel, and sand as a filter here.

Rainwater vs. Groundwater

There are two main types of water – rainwater and groundwater. Groundwater is found underground in aquifers, while rainwater can collect on the surface. Rainwater is less contaminated than groundwater since it hasn’t been exposed to the earth. Rainwater, conversely, can become contaminated by pollutants in the atmosphere or on the ground. 

How to Purify Rainwater?

  • Collect rainwater in a clean container.
  • The water should boil for at least one minute, 5 minutes is better.
  • Filter the water through a coffee filter, cheesecloth, or clean cloth to remove any dirt or debris.
  • Allow the water to cool before drinking it.
  • Store any unused water in a clean, covered container.

Following these instructions may guarantee that the rainwater you’re drinking is safe and clean. You can also use this approach to purify groundwater before consuming it.

How Can You Purify Rainwater in a Non-Survival Situation?

If you collect rainwater in a tank at home or at a more permanent camp there are a few different ways that you can purify rainwater, both in the tank and before you drink it.

How Can You Purify Rainwater in a Non-Survival Situation
  • Treat your rainwater with a product that prevents algae and bacteria growth.
  • Install a first flush diverter, this helps prevent any dust and dirt build-up from being washed into the tank on the first rain
  • Treat your rainwater with an ultraviolet light filter.
  • Treat your rainwater with ozone gas.
  • Treat your water with chlorine.

These are a few of the most common methods of rainwater purification.

Potable vs Non-potable Water

What is Potable water? The word “potable” comes from the Latin word potare meaning “to drink” and abilitas which meant “ability or able” so the word literally translates as drinkable. The Romans knew that people needed clean potable drinking water, so they built aqueducts to bring potable water from fresh mountain streams into the cities.

Potable vs Non-potable Water

Potable water is safe to drink, while non-potable water is not. Non-potable water can contain contaminants that make it unsafe to drink. When using rainwater for drinking, it’s essential to be sure that it’s pure.

Sedimentation and Filtration

Sedimentation is the process of removing solid particles from water. We usually let the water settle so the particles can settle to the bottom. Sedimentation and filtration are two methods of water treatment. They’re both effective at removing contaminants from water.

Sedimentation is more effective at removing larger particles, while filtration is more effective at removing smaller particles. Sedimentation is a passive treatment method, while filtration is an active treatment method. We use Sedimentation as the first step in water treatment. This process is done with the help of filtration to remove smaller particles.

Preventing Algae & Bacteria Growth

One of the most common problems with rainwater is algae and bacteria growth. Algae and bacteria can grow in rainwater tanks, especially if the water is not treated correctly.

Preventing Algae & Bacteria Growth

There are a few things you can do to prevent algae and bacteria growth in your rainwater tank

  • Clean your gutters regularly, so leaves and other debris don’t end up in your rainwater tank.
  • Install a first flush diverter
  • A diverter is a mechanism that diverts the initial water flow from your roof away from your tank. This initial flow of water is usually the dirtiest.
  • Treat your rainwater with a product that prevents algae and bacteria growth. There are a few different products on the market, so be sure to research to find one that is right for you.

Primary Filtration

The first stage in essential filtration is to remove large particles from the water. You may get rid of the odor by utilizing a sediment filter. A sediment filter is a type of filter that traps and removes particles from water.

The water’s second filtration stage is to remove tiny particles from the water. For this process, we can do it with a carbon filter. A carbon filter is a type of water filter that uses charcoal to remove pollutants from the water.

Reverse Osmosis

Reverse osmosis is a technique of pushing water through an exceptional membrane. This process removes dissolved minerals, bacteria, and other impurities from water.


Deionisation is a process that removes dissolved minerals from water. Usually, we use this process to treat water for industrial use.


The use of ultraviolet radiation to destroy germs and other microscopic organisms in water is known as UV disinfection.


Ozonation is a process that uses ozone gas to disinfect water. Ozonation is a powerful disinfection method that is effective against various microorganisms.


Chlorination is a process that uses chlorine to disinfect water. Chlorination is a widespread disinfection method against bacteria and other microorganisms.

Keeping Rain Water Fresh During Dry Periods

If you live in an area with many dry spells, you may need to take extra steps to keep your water fresh.

These are a few tips to help you keep your water fresh during dry periods.

Benefits of Rainwater Harvesting

If you’re in a long-term survival situation, adequate rainwater harvesting is an essential part of any water solution. Setting up your own system to capture and store freshwater from sky rains or dew points will ensure that you have ongoing access to fresh potable water.

Benefits of Rainwater Harvesting

In the home garden, rainwater harvesting can also help to reduce flooding and erosion. Water flows slower across porous surfaces allowing the water to seep into the ground. Another way to harvest rainwater is to create a rain garden. A rain garden is a shallow depression where we can plant native plants.

Clean Water Begins With Best Practices

The best way to reduce pollution is to follow best practices regarding handling water. It includes not dumping chemicals or other pollutants down the drain. Improperly disposing of hazardous materials can lead to contamination of the water supply.

You can also help to reduce pollution by conserving water. We can do it by using drought-tolerant plants in your landscaping and fixing any leaks in your home.

What is Stormwater?

Stormwater is water that did not percolate into the ground due to rain or melting snow. It flows over the land’s surface and can pick up pollutants like oil, dirt, and chemicals. Stormwater can also cause flooding and erosion.

What is Stormwater

It’s important to manage stormwater properly to reduce its environmental impact. One way to do this is to create a rain garden. A rain garden is a shallow depression where we can plant native plants. Another way to manage stormwater is to use green infrastructure. Green infrastructure is a system of using vegetation and other natural elements to collect water. We can use it to reduce flooding, erosion, and pollution.

Green infrastructure is a great way to manage stormwater because it’s good for the environment and can save money.

We All Rely on Clean Water

Water is essential for life. We rely on it for drinking, cooking, and cleaning. When water is polluted, it can cause severe problems for people, animals, and the environment.  That’s why we must do our part to reduce pollution. Following the tips above, you can help keep our water supply clean and safe for everyone.

Can I Filter Rainwater to Drink?

Yes, you can filter rainwater to drink.


To sum up, knowing how to purify rainwater is very important. This guide has given you the steps on how to do so. Be sure to drink safe water by following the above steps!

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