Q&A for How to Make a Water Filter

Each time the water passes through a different layer, it becomes cleaner. First, the gravel layer catches large pieces of debris, such as twigs, leaves, and bugs. Next, the sand layer catches smaller particles, such as dirt and grit, and makes the water look clean. Finally, the charcoal layer gets rid of bacteria and some chemicals.

Activated charcoal is made a little differently from regular charcoal. It has oxygen added back to it. This makes it more porous thus better at filtering impurities. It is commonly used in water filters and aquarium filters.

Unfortunately, filtering is not enough. Some types of microbes, bacteria, and viruses are too small to be filtered out. They can only be killed by very high temperatures.

It has to be activated. You can buy it in pet stores or grocery stores in the section for fish supplies. Don't buy the pellets - get the crushed kind.

Yes. Without the activated carbon, the bacteria and chemicals in the water will not be filtered out.

The sand layer helps catch the smaller particles, such as dirt and grit, and makes the water look cleaner.

Activated charcoal works through adsorption. This means that all that stuff in the water that we can't see binds chemically to the carbon. By the time the water passes through all the carbon, it has fewer chemicals and bacteria in it.

The layers are porous and water, being a liquid, has the ability to move those layers.

Yes, it does. I used this method to make my water filtration system for my project.

The filter can be used more than once, but it is better if you replace it after every use, as the coffee filter may be contaminated and unhygienic.

Yes. The layers are arranged by particle sizes. If you put smaller particles on the top, it would cause clogging for the filter, and render the bottom particles useless.

You can use other materials that are similar to a coffee filter, such as a cheesecloth. Make sure the cloth doesn't contain any dyes or they might contaminate the water.

If you boil it, then there will still be small parts such as twigs or leaves. After this, you collect the evaporated water onto cold metal to condensate it, and eventually wait for it to pour into your bottle. It may be easier to just collect a few stones and activated charcoal and pour the water through them, then boil it for one minute.

Use water from local bodies of water, to see how much it purifies.

Charcoal removes the dirt from the water. Boiling will kill the bacteria, but won't clean the water.

No, although layers in the filters are effective, most microbes, bacteria, and other harmful things are too small for the layers to remove have, so the water has to be boiled in order for it to be safe to drink.

The sand and gravel filter out things like sticks, grass, and dirt that would otherwise get in the water because the activated charcoal doesn't filter items out of the water, it filters out bacteria and chemicals.

Fill the portion of the filter where the bottle gets thinner, or the bottom third. Make sure the gravel is crushed up. Tip: After cutting the bottom off of the bottle, draw 3 small tick marks evenly spaced along the side of your bottle. Fill from the coffee filter to the first tick with activated charcoal, then pour sand into the bottle until the next mark. Finally, pour in gravel until the last tick mark. Leave the last portion empty so your filter won't overflow as you pour more water in.

If you are filtering water and it has debris in it, you would want to get rid of that before boiling. Boiling the water is just for getting rid of the bacteria and viruses that cannot be filtered.

That really depends on how much water you filter through it. Once the filter becomes less effective, you should replace it.

There's a possibility the water would be clear, depending on the unfiltered water you initially poured in the filter. However, it may still contain bacteria and chemicals that you cannot discern.

You can use any type you can find as long as it is activated charcoal. It's best if it specifies "regular" on the package.

Ask your local pet shop experts.

You can get sand from almost any plant store, or simply collect sand from a nearby beach and clean it. But, wet sand cannot be used for the filter, as it may make dirt in the air stick to it and pass through the filter, and wet sand is harder on the filter than dry sand.

Yes, you can. I have tested all of these filters with lake water from my backyard for my science fair project. I then boiled the water and used a home drinking water test kit to see if the water was drinkable and it passed the tests twice.

Normal, crushed charcoal works, but not nearly as well as activated charcoal.

No. Activated charcoal is created in a manufacturing process by adding oxygen. This makes the charcoal very porous, meaning it has a very high surface area. Ordinary charcoal doesn't have that.

Use a large properly cleaned out barrel or drum, and do the same method, but with larger measuring devices, tools, and equipment.

You should able to find activated charcoal at major retailers, both in person and online, or at pet supply stores.

No. Activited charcoal has special properties that make it ideal for filtering out small particles.