All water must be treated in some way before you consume it. In this article you will learn how to make four different types of homemade water filtration systems which you can use at home, camping, or even as a homemade water filter science project.
Most of these homemade water filter projects will kill pathogens, but they will not make seawater, urine, or chemically tainted water drinkable. That requires distillation.
DIY Gravity Water Filter
This is a reliable way to make a homemade water filter without charcoal. It uses porous ceramic which has many tiny holes that filter out contaminants as water passes through it. It is essentially a DIY Berkey water filter.
You can’t make the ceramic filter element, but sourcing one is not an issue in most places, and you can store unused filters for a long time.
This homemade water purifier is cheaper than buying a commercial gravity filter, and you can adapt it to what you need you need. You can put one in your rain barrel, for example, which creates an all-in-one DIY rainwater filter system.
What You Need
- A candle or pot ceramic filter element. Ensure it meets drinkable standards.
- 2 food-grade buckets.
- A spigot.
- A drill.
How to Make a Gravity Ceramic Filter
Bucket 1 is the top bucket. This is where you will put the unfiltered water. Bucket 2 stores the filtered water.
Create a hole in the center of the bottom of bucket 1 to fit the ceramic filter, then attach the filter so the nipple goes through the hole. It must fit flush, so no water can sneak through without passing through the filter.
Cover the filter with the cheesecloth to trap larger particles. This will increase the life of the filter. It is not shown in the image.
Put a hole in the lid of bucket 2 so it lines up exactly with the hole in the bottom of bucket 1. Drill a hole 5cm (2in) from the bottom of bucket 2 to fit the spigot. Follow the manufacturer’s instructions to fit the spigot.
Place bucket 1 on top of bucket 2. The filter’s nipple needs to pass through bucket 2’s lid. Pour water into bucket 1. It will pass through the filter into bucket 2, and you can then drink it. It will take a while to filter.
Maintain the filter element as per the manufacturer’s instructions.
Bio Sand Filter
A bio sand filter uses sand, gravel, and a natural biological process to filter out contaminants. Once built, it takes a minimum of 10 days to produce drinking water.
The components of a bio sand filter are as follows, from the top down:
- Lid. Prevents contaminants from entering the water.
- Reservoir. Holds unfiltered water.
- Diffuser. Spreads the water evenly, minimizes disturbance to the bio-layer, and keeps large particles from entering the system.
- Resting water level. Prevents the sand from drying out, which helps create the bio-layer.
- Bio-layer. Good bacteria to clean the water. It develops in the top 5cm (2in) to 10cm (4in) of sand.
- Filtration sand. Removes more contaminants. It needs to be 0.15mm in particle size and 15cm in depth.
- Separation gravel. Prevents sand from going into the outlet tube.
- Drainage gravel. Supports the first layer of gravel and helps keep sand from going into outlet tube.
- Outlet. Transports the clean water to the clean water container.
- Clean water container. Stores the clean water ready for use.
What You Need
- A 20L (5gal) food-grade plastic drum with lid.
- 1 extra lid or other food-grade piece of flat plastic for the diffuser plate.
- PVC piping, joiners, and end caps.
- A drill.
- A 2mm drill bit.
- Rubber grommets.
- A food-grade bucket with a lid.
- River rocks.
- Pea gravel.
- Fine sand.
- Water. Use the cleanest non-potable water you have available.
Wash everything well, including the gravel and sand.
How to Make a Bio Sand Filter
Find somewhere flat and out of the way that is still convenient to access. Build a low stand from bricks and place the drum on it. This is its permanent position. Moving it will disturb the filtration layers.
To make the outlet, drill a bunch of small holes in a couple of short pieces of PVC pipe and join them together in parallel. Make sure they fit inside the drum. The holes let the water exit the filter without clogging the outlet tube. Clean any plastic bits out of the pipes and attach tubing to transport the water out of the filter.
Drill a hole in the bottom of the drum for the tubing to pass through and use the grommets so it doesn’t leak. Plug the tubing during the setup phase. Test it to make sure there are no leaks.
Use the flat piece of food-grade plastic to make the diffuser plate. Cut it so it fits snug and flat inside the drum at the right place. There must be 5cm (2in) of space between the sand and the diffuser for the bio-layer to form. There must also be enough room between the diffuser and top of the drum to add unfiltered water.
Once you have the size right, drill a bunch of small holes in the plate.
Mock fit the diffuser where you want it to go, and test it. Mark a fill line for the sand in the drum.
Fill a quarter of the drum with water, then cover the outlet with an even layer of river rocks. Add a 3cm- (1 in) layer of pea gravel on top of the river rocks, then add more water.
Add the filtration sand up to the line you made before. Add more water as needed so the sand is always entering water, and pour the water through the diffuser to help keep everything even. As you add the sand, use your hand to help spread it out.
Set the diffuser plate in place, then fill the drum up to the top with water and put the lid on.
Unplug the tubing so water will come out of it. Direct it into an empty bucket, but not into your clean water container.
For the first couple of days you need to add water continuously, until all the components settle. If sand settles more than 5cm (2in) below your sand mark, add more sand. Always keep at least 5cm (2in) of water above the sand.
It takes a minimum of 10 days for the bio-layer to form. Do not drink the water before then, but feel free to use it on your garden.
Do not add any chemicals (purification or otherwise) to the filter. If you want to treat it further, add the treatment to the post-filtered water.
After 10 days, test the water to make sure is it good to drink. If it is, direct the tube outlet to your clean water bucket. Create a hole in the lid so the tube can enter but nothing else can. Label the clean water bucket and never use it for anything else.
If you create a constant flow inlet (from a stream, for example), make sure you also create an overflow outlet by drilling a hole near the top of the drum and using tubing to direct the excess water to wherever you want it to go.
These instructions are an adaption of the HydrAid Bio Sand Filter:
Cleaning Your Bio Sand Filter
If you notice the flow getting low, the filter is probably clogged.
Pour a bucket of water in and swirl the upper layer of sand with your hand in a circular motion. Remove the dirty water created from swirling, then smooth out the sand on top. Repeat this “swirl and dump” procedure until the flow rate is restored.
It will take several days for the good bacteria to reform. Retest the water before drinking it.
You can clean the outlet, diffuser plate, lid, and outside without dismantling the whole thing. For everything but the outlet, use bleach or soap, then rinse with clean water.
Clean the outlet by back-flushing it—that is, forcing clean water through it in the opposite way from the one in.
DIY Charcoal Water Filter
This homemade charcoal water filter is commonly known as a layer filter. The water passes through layers, from coarse to fine, to remove contaminants. What you use for each layer depends on what you have. The more different layers you have the better.
To make a homemade charcoal filter from a plastic bottle, cut the bottom off and turn it upside down. Place a layer of cloth on the bottom, which was the nozzle. This prevents the other layers from falling out.
Fill it up with materials, from fine to coarse. Charcoal is a great bottom layer because it can absorb chemicals. In a survival situation, even charcoal (not ash) from your campfire will work, although not as well as activated charcoal.
The complete layer system may look something like this:
Sapwood is a good bottom layer instead of or as well as charcoal. It’s slower to filter, but removes more micro-organisms. If you “cork” the nozzle of a bottle with it, expect four liters of drinking water a day. The bottle must be sealed tightly.
If you need a survival water filter and you don’t have a bottle, you can construct a tripod and use several pieces of cloth to hold each layer.
SODIS Water Treatment
The SODIS method isn’t a filter like the other projects in this article. SODIS uses the UV rays from sunlight to treat water. This is an effective, chemical free, and low-cost DIY water purifier.
Ideally, you will filter the water first, then use the SODIS method to further purify it. However, if no other filtration method is available, using the SODIS water treatment method on clear water is sufficient to make water safe to drink.
The problem with the SODIS method is that it is weather-dependent and slow. On a sunny day, which is ideal, it takes six hours to treat a 2L bottle of water.
SODIS works best in places within 35 degrees of the equator.
What You Need
- A transparent PET bottle no larger than 2L (0.5gal).
- Clear water.
The bottle must be clean and damage-free. Undamaged and uncolored soda bottles are popular choices.
Use the clearest water you can find. It must be clear enough to count your fingers on the other side once the water is in the bottle. If you don’t have water that clear, you can run it through a fine cloth and/or a bio-filter.
SODIS Water Treatment Directions
Wash the bottle for the first use and fill it three-quarters full with water. Put the lid on, shake it vigorously for 20 seconds, then fill it the rest of the way to the top.
Check it for clarity and leave it in the sunlight for the required amount of time:
- Sunny = 6 hours
- Partly Cloudy = 24 hours
- Very cloudy = 48 hours
- Raining = Not effective. Drink the rainwater instead.
You can maximize the sunlight by putting the bottle(s) on a reflective surface, like aluminum foil or a metal sheet, and/or sloping it/them towards the sun.
Once the water is ready, store or drink it straight from the bottle. Transferring it increases the chance of contamination.
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DIY Water Filter Conclusion
All of the above homemade water filter’s are effective and relatively cheap ways to create drinkable water both at home and in a survival situation, but only if the water source is not too tainted to begin with.
Using them with rainwater is a pretty safe bet, but it is always wise to use a water-quality testing kit that can test for bacteria, lead, pesticides, nitrites, nitrates, chlorine, hardness, and pH.
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