How To Filter Water To Survive A Disaster

Marissa Newby
5 min readDec 16, 2021


Stockpiling water may not be part of your home or family’s emergency and disaster planning. Rest assured, though, that having clean drinking water is necessary to survive. Depending upon your water source, simply boiling water may not be adequate enough, or you may not have a safe way to start a fire, especially if you are stranded in your home or car. Planning ahead can save your life. Warning: drinking unsafe water, even if you filter it, can still result in diseases or illness. Please discuss any illness with your physician. This information is to be used in case of an emergency or dire situation and it is not intended to replace known clean water sources.

Photo by Pixabay from Pexels

What You Will Need

Start with 3 watertight containers — usually plastic, this can be buckets, bottles, milk jugs, etc. Whatever you use needs to be kept clean and away from chemicals in your home, bag, or vehicle (I suggest keeping them in all 3 because you may someday need them in the most unexpected ways).

Get cloths, or clean shirts, that can hold sand without letting it fall through the fibers. Get sand, you can find filter sand in some unexpected places. Look for sand on sale in big box stores during pool season, or go to pet stores and find sand or sand substrate. You can also use sand from a beach nearby but you have to wash it and sift it first, so this natural gathering needs to be done before you lose access to clean water or that makes this step more challenging.

Gather gravel, this can be landscaping rocks if you need to save time. These rocks will have to be cleaned. You can also purchase gravel in stores, or find it in creeks or riverbeds to clean and use later or gather it from your surroundings. Bear in mind that rocks, sand, and other natural materials that are porous or in the elements can have bacteria, fungi, and other contaminants attached. Wash everything you gather before you have to use it to filter your drinking water.

Finally, gather charcoal. You can make charcoal by burning wood over a fire until it is charred and then crushing it. You can also have charcoal ready by purchasing it. If you have trouble finding charcoal, you can often find it in arts and crafts stores. Crush the charcoal into a finer powder.

How To Filter

This process takes time and patience. Early gathering can lead to greater success and shortened periods without clean water. Always keep in mind that this is not a foolproof method and you are still at risk of disease unless you utilize a commercial filter or safe and tested municipal water source.

Start by gathering your water, avoid sources near factories, sewage areas, or run-off areas from mining or industrial operations. Standing water is also ok. You can, in some areas, also use rain catchment systems for this step if you have a container and piping for it. Check your local laws or, if this is an emergency, use your best judgment. Allow this container to sit for a few hours to let any sediment settle to the bottom of the container.

Place the cloth or shirts over the opening of your container after the solid matter has settled then place another shirt or cloth over the opening of a clean, empty container. On top of the cloth on the second container, place your rocks. Pour the water from the first container into the second container slowly, allowing water to wash through the rocks.

In the third container, or after the first container is rinsed clean of sediment, place a third cloth or shirt over that opening and put sand on the shirt or cloth. Pour the water that was filtered through the rocks into the sand filter and allow the water to settle again.

Finally, in a clean container, place a shirt or cloth over the opening and put your charcoal over the opening and cloth. Pour the water over the charcoal and filter it one last time. You can repeat these steps if you have the materials to ensure that the water is filtered properly.

Creative, Hands-Off Solution

This only works if you have a power source and pre-plan. So, ahead of time, you will have to gather these materials and this method is more cost-prohibitive. You will start by gathering a 10-gallon or larger aquarium. Purchase a 5 or 7 stage RO/DI aquarium filtration system. You can also use smaller, cheaper versions. Make sure the filter can clean at least 20 gallons per minute. A good rule of thumb should be to find a filter that can filter twice as much water as you have in the tank. Leave the bottom of the tank empty, without any substrate, so that you can see any sediment that settles and avoid drinking it.

The smaller, cheaper filters often have external media that you have to place. There are filter pads or available to be purchased along with the filter itself. You can also purchase filter media that will help add filtration. Moving water over the correct filtration elements is a safe way to try and clean it for drinking.

I tested my system using two different filters to confirm the 3 major types of filtration were done correctly. You must have mechanical filtration (water moving over media, usually some form of ceramic or rock in aquarium filters, in your makeshift filter this is done by pour-over, rocks, and sand). Biological filtration is the next necessary step, this is conducted inside aquarium filters using biological filter media. Finally, chemical filtration is achieved by charcoal.

The Marineland Bio-Wheel filters have all 3 types of filtration and this can render your water quite clean after running for a few hours to recycle the water and allow the sediment to settle on startup or refill. This is a viable, cost-effective option. However, if you have the coin, my experience is that canister filters are superior. Fluval aquatics makes, arguably, the most expensive consumer-grade filters but they are proven to work for aquatic creatures. You can find variations of these canister filters on the market. Make sure you buy extra filter pads, filter media, and charcoal media that match your filter set up.

These filters and aquarium systems require maintenance, be prepared for that. They also require a power source. So, this is a self-limiting system. If you are in a pinch you can use the makeshift filter. If you have the luxury of electricity and space, consider building a system. When initially filling this system, ensure you rinse the charcoal media and then place it into the filter to run for a few hours before attempting to drink that water. Upon refill, you also need to wait a few hours to ensure the filter has had time to work

When removing water for drinking or cooking from the aquarium system, use a clean vessel or scoop. Introducing contamination in this system or other filtration efforts will ruin what you have filtered. You can cross-contaminate water.


FEMA addresses different types of safe filtration for water systems during emergencies. The website has several informational resources on how to render your water safe during disasters. The CDC also offers filtration guidelines with measurements for chemicals that you can use if you have them in your stockpile.



Marissa Newby

Blogger, horror writer, poet, feminist, existential crisis