Water filters and purification

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A water filter removes impurities in water using a fine physical barrier, a chemical process, or a biological process. Filtering water clarifies water (makes it cleaner and clearer), but does not purify it. Water purification is the process of making water safe to drink.

Several Cub and Scout badges can involve making a water filter:

  • Silver Wolf - "Find out three things that can cause water pollution and show how you could possibly undo pollution in water" and also "Demonstrate how clean or dirty the water is that you use.
  • Gold Wolf - "Understand the importance of always drinking clean drinking water. Demonstrate how to make water safe for drinking, if no clean water is available."
  • Cub Civil Emergency Badge - "Explain the importance of clean water and demonstrate how to purify water using a funnel and natural materials."
  • Conservation Scoutcraft Badge - "Participate in a conservation project covering ONE of the following: clean water"
  • Survival Scoutcraft Badge - "Demonstrate any method of rendering muddy water fit for human consumption."
  • Backwoodsman Scout Interest Badge

How to make a water filter

Making a water filter at home or at cubs and scouts is easy.

What you'll need

  • Plastic drink container. A 2 litre cooldrink bottle is ideal.
  • Knife and scissors
  • Nails
  • Pebbles (around 1cm in diameter)
  • Charcoal (activated charcoal, or already burnt charcoal from wood)
  • Clean sand
  • Cotton or coffee filter


  1. One method is to cut the cooldrink bottle in half, and invert the top of the bottle into the other half of the bottle. Use a knife carefully to cut a small section of the bottle, and carry on with the scissors. Alternatively, you could simply use one half of the bottle, where you'll pierce the bottom with a nail so that the filtered water can drip out.
  2. Plug the bottle neck with cotton wool or a coffee filter
  3. Add the fine clean sand. If the sand isn't clean, first rinse and sieve it before adding to your filter.
  4. Add the charcoal. Activated charcoal is best if available.
  5. Add the pebbles to the top.

Water Filter Bottle 1.jpgWater Filter Bottle 2.jpg

Now your water filter is ready to try out. Take some muddy water with a few leaves in and see what comes out at the bottom. Please be aware that while the water is cleaner, it may still have harmful organisms inside. You should boil the water for 5 minutes or purify the water before drinking it.

How it works

  • The larger filtering items such s pebbles are on the top, and these filter out larger dirt such as leaves and sticks.
  • The charcoal further filters smaller impurities, and is known to absorb toxins using chemical absorption.
  • Fine sand filters out tiny pieces of dirt and mud
  • The cotton wool or coffee filter is the last layer, and this helps clear the colour of the water.

Water purification

Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from water. The goal is to make drinkable water.

  • Method 1: Rapidly boil the water for at least 5 minutes.
  • Method 2: Make use of store bought water purification tablets. Follow the instructions on the box in terms of how many tablets to use per litre of water, and how long before you may drink the water. The active ingredient in water purification tablets is typically chlorine, chlorine dioxide or iodine.
  • Method 3: Solar water disinfection - using solar energy to remove biological contaminants from water.

Paper towel filter

You can make a really simple filter using two containers and some paper towel. Put the dirty water in the first container, and put that container slightly higher than the other container. Put one end of the paper towel into the dirty water, and the other into the empty container. The paper towel acts as a siphon and a filter at the same time, and transfers the water into the lower container - with most of the dirt removed. Depending on the paper, it will take an hour or two to filter a cup of dirty water.


Filter Before.jpg


Filter After.jpg

See also