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I have recently become interested in building my own home-brew water filtration unit; during my online research on the subject, I came across active carbon (aka activated charcoal). It seems like it may be a great addition to my current ideas, although I have a few questions:

1: Where can I get active carbon that is okay for human consumption? (It's not like I will be taking it in directly, although drinking water will pass directly through it).

2: How can I effectively use the active carbon, and also use it efficiently?

3: What is the filtering lifespan of active carbon? (How long can it effectively clean water? For a given amount of carbon, and water).

Thank you in advance :)

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3 Answers 3

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Activated carbon is basically charcoal that has been heated to a high temperature without igniting it. Best way to make it is to get hardwood (maple, oak - the best, hickory) and seal the wood in foil, with as little trapped air as possible (you don't want to have the wood start burning). Bake the wood at 500F or heat in a fire until there is no more smoke coming out. When you open the packet, you should see lumps of black charcoal. When you get ready to activate the charcoal for water filtering, reheat the charcoal at 475F to release absorbed air. You can pack it into a tube as Brandon describes, but you will want a finer mesh screen than most window screen material. Most brew suppliers have brass filtering screens that are round and fit nicely into the pipe. BTW - be certain to clean the PVC or buy food grade PVC to start with (not all PVC pipe is rated for drinking water). The tygon (clear) tubing that most brew suppliers sell works great as an alternative to PVC. Just get the largest bore that they sell, pack the charcoal into the tubing with sterile cotton balls to keep the charcoal from leaving the tubing. We use this in the lab and on work trips to filter pre-sterilized water. The tubing is easy to transport, hard woods can be found all over the world, and charcoal is easy to make. One quick and dirty way to test the filtering is to put the filtered water to a clear glass, turn out the lights and shine a flashlight through it. Suspended particles will cause what is know as Raleigh scattering and you'll see colors appear as the light shines through as the particle concentration increases. But honestly, a Brita or Pur filtering system is usually cheaper and easier to use in the long run.

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Wow, thank you! :) Very informative. –  James Litewski Apr 23 '11 at 7:08
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I built a pretty simple filter apparatus using a universal refrigerator filter I found at Lowes. It has 1/4" compression fittings, so I just got the proper hose and adapters to convert to 3/4" compression (garden hose) which I then have a faucet to garden hose adapter, and I just hook it to my faucet and run it into my kettle. cost about $35 total. A lot easier than messing with $115 worth of granulated carbon.

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http://www.amazon.com/Granulated-Activated-Carbon-1-cu-ft/dp/B0017677O8

You could probably also use the products labeled for treating ponds or fish tanks, since AFAIK it's all the same carbon - usually made from coconut shells. For water filtering, especially if you're using a gravity-feed, look for 12x40 or 8x30 grain sizes.

To use it, I would just make a housing from 2 or 3 inch PVC pipe with a screen at the bottom - using whatever screen or wire mesh you can find around the garage, with a coffee filter between the screen and the carbon to hold the filter media in place. Use PVC endcaps as required.

Testing with chlorine strips would tell you when it's time to refill the charcoal. The amount of water that it can filter will depend on the concentration of impurities in the water as well as the particle size of the carbon, so you'll have to do empirical testing with your setup to determine how long the carbon lasts.

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Thank you! Your comment should be a big help, I didn't even think about using chlorine strips, that's a great idea. –  James Litewski Apr 12 '11 at 22:44
    
James, you should mark this question answered if Brandon it answered everything you were looking for. Just sayin... ;-) –  markskar Apr 13 '11 at 20:28
    
Yeah sorry, I haven't had my computer for some-time, so I'm just getting a chance to look at my answers.. –  James Litewski Apr 23 '11 at 7:06
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