View Full Version : Emergency water filter viability

2005-07-12, 06:02
This is just an idle thought, but I figured I would run it past you, as you would be able to point out any problems, or if my thought wouldn't work at all.

My idea is a filter made with things I would be likely to have with me.

What if I took a bread sack, ripped some holes in the bottom*, shoved it into a sock, and filled it with charcoal** from a firepit.
Pour water in the top and catch what comes out the bottom.

*this would force the water to travel through the charcoal and not around it (as it would do if I put the sock inside the bag)
**black coals no grey or white ash - don't want to leach out lye.

I know that many water filters only have a sediment filter and an activated carbon filter, this would basically be the same thing.

2005-07-12, 09:16
Interesting idea. Two possible problems:

1. The water would probably travel around and between the pieces of charcoal.

2. Even if the water didn't travel around it, would it even be possible to force water through such charcoal?


2005-07-12, 12:09
I think maybe if you pulverized the charcoal a little so that it ended up in the sock and the sock was thick like a smartwool sock then that would help. I am not sure I would want to give up a sock so easily but maybe some other piece of cloth or even some moss. The right kind of moss might even work without charcoal but probably to slow. The plastic bag with just a few small holes is a good idea. I think a nylon stuff sack would also leak slow without holes. Of course if you had charcoal you probably have fire and so you should be able to boil the crap out of any old mud muddle. The bag filter is still a good idea though anytime you are drinking out of mud puddles even if you are using Aquamira or Boiling or a real filter.

2005-07-12, 14:16
That'll only affect the taste a bit. What makes water filters work is that the water is forced through a fine sieve that strains out the crud and cooties and passes through the charcoal where the charcoal can adsorb chemicals. Without the constraints of a pressure vessel forcing this to happen, you are going to have little effect.

There are gravity filters available that do not rely on a pressure vessel, Katadyn makes several, but gravity itself provides the pressure that pushes the water through the filter element. The Katadyn/PUR Hiker can use a siphoning effect to operate hands-free as well. But you aren't going to cobble together an effective water filter from campfire leavings, a sock and a plastic bag. Toss in some fabric coffee filters, a plastic bottle and a roll of duct-tape and you might have a different story though.