How to Make a Homemade DIY Water Filter

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Want to filter your water in the wilderness, make your own emergency preparedness solution, or just get stuck into a fun project with the kids?

In this guide, we’ve shared the process that we personally used to make a highly effective DIY water filter, using just a few simple tools and natural filter media. 

Note: There are a few different methods of making DIY water filters, and several types of materials you can use. We’re sharing instructions for the filter we personally made ourselves, which uses multiple layers of filtration, including gravel, sand, and activated charcoal, to remove various impurities from water. 

📝 What You’ll Need

You will need: 

  • A plastic bottle
  • Knife
  • Gravel of different sizes
  • Sand, both fine and coarse, if possible
  • Cotton, bandana, sock, or similar
  • Activated charcoal

✂️ Step 1: Cut the Bottom Off the Plastic Bottle

Take the plastic bottle and cut the bottom inch or so off, using a knife. 

🔄 Step 2: Flip the Bottle

Next, remove the cap from the bottle (if you haven’t already), or, if you plan to use a coffee filter in step 3, stab a hole in the lid using a knife or a sharp pair of scissors. We removed the cap as we used cotton balls in step 3 instead. 

Flip the top of the bottle upside down and place it in the separated bottom for stability, with the cap end pointing down. This will prevent the bottle from tipping over when you add your filter materials.

☁️ Step 3: Add The First Material to the Bottle

Now you can start adding materials into the bottle. 

The first material, which will go at the bottom, needs to be able to hold everything else above it.

If you have them, cotton balls work great for this purpose. You can also place a coffee filter over the bottle opening, so that the excess material of the filter overlaps around the bottle’s sides. Then, put on the lid and tighten it to secure the cap.

If you’re in a survival situation, anything made of cloth, like a bandana or even a sock, will work just fine.

🔮 Step 4: Prepare & Add the Charcoal

The next material you’ll add is charcoal. 

If needed, break down the charcoal into small pieces (we found it easiest to use a hammer, but you could also use a rock). You want to fill as much of the bottle’s surface area with the charcoal as possible. 

You can now pour the charcoal on top of the first layer. This layer should be about 1 inch in thickness. 

📥 Step 5: Add A Layer of Fine Sand

Next, add a layer of sand. Any sand is fine, but the finer and smaller the grains, the better – fine sand should be able to remove smaller contaminants from your water.

Also don’t use processed, dyed craft sand, which could introduce chemicals into your water.

Again, this layer of sand should be around 1-inch thick

📤 Step 6: Add Coarse Sand on Top

If you can find it, add a 1-inch layer of coarse sand on top of the fine sand. 

In our own experience making this filter, we found that using both coarse and fine-grained sand means you can filter water through two separate textures, allowing for more diverse, thorough filtration. 

🪨 Step 7: Top With Gravel

Pour gravel into the bottle, stopping once the top surface of the gravel is one inch away from the cut part of the bottle. 

Again, you can use both chunky and fine-grained gravel here to provide separate layers of filtration.

🔲 Step 8 (Optional): Add a Top Strainer

Lastly, if you have the resources, cover the top layer with a coffee filter or a cloth (such as a cheese cloth or bandana). 

This is an optional step but it’s great for straining large debris from water.

🔎 Test it Out!

Your filter is now ready to test. For this, grab a clean cup or use the bottom of the water bottle you already cut off to catch the filtered water.

Carefully pour your dirty water into the top of the filter and watch it work its magic.

Our Tip: Slow, steady pouring is best. Pause between adding water to wait for the water level to fall below the top of the gravel.

Water will travel through the filter layers, becoming cleaner as it goes. Within a few minutes, it’ll start to fill the bottle.

🔂 A Note on Double Filtering

If you have a dirty or turbid water supply, you might need to filter water several times through your bottle filter. 

To do this, wait for all the water to fill the cup, then put the water bottle onto another cup and pour your original batch of water back through the bottle.

📑 Final Word

We’ve tried a few different DIY water filters, and we’ve found that in our testing, this one worked best. 

It’s important to keep in mind that while this homemade filter can remove some impurities, it’s not a guaranteed replacement for commercial water filters or municipal water treatment. There’s also no way to know for certain that the filter has removed certain contaminants from your water unless you conduct before-and-after water quality testing. 

So if you’re relying on this for drinking water and you’re using a water source that’s potentially microbiologically contaminated, you’ll need to boil the water for three minutes to make it potable (safe to drink) after you’ve filtered out the contaminants. That’s because microorganisms like bacteria are too small to be trapped in any of these homemade water filter materials.

If boiling isn’t an option, you can also chemically disinfect your water with iodine tablets or unscented bleach, or sterilize it using UV. 

  • Brian Campbell
    President & CEO, CWS, CWR

    Brian Campbell, a WQA Certified Water Specialist (CWS) and Certified Water Treatment Representative (CWR) with 5+ years of experience, helps homeowners navigate the world of water treatment. After honing his skills at Hach Company, he founded his business to empower homeowners with the knowledge and tools to achieve safe, healthy water. Brian's tested countless devices, from simple pitchers to complex systems, helping his readers find the perfect fit for their unique needs.

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