tripod lashing

instructional article

Bandana Use #147: Water filter

The internet is full of tips and tricks and gadgets. Half of which make me wonder if they really work. Some I know for a fact do not work. So before I repost anything I like to make sure it's legit. One I've been wondering about for a while is this diagram I found of a water filter tower made from 3 bandanas, and layers of grass, sand and charcoal. 

bandana water filter_survival bandana

On my last camping trip I decided to put it to the test. I did some modifications for my design. I wanted to limit it to one bandana, and simply layer the materials in that bandana. I did a base layer of sand, then rocks, then dry grass. MAJOR FUNCTIONALITY NOTE!!! This type of filter is NOT meant to make water safe to drink. It does not remove any kind of pathogens, or water born illness. It is meant to remove sediment making it easier to prepare for boiling or some other form of treatment. 

I started by making a 4 sided "quadpod". I make this the same way I would a tripod, but with an extra pole (for those really bad at math). Start with 4 equal length branches. 


Tie a clove hitch around the first branch. Then weave the rope over and under the other branches. When you get the end, weave the rope back the other way. Do this 3-4 times. You can simply wrap the rope around the outside of all the branches, but the weaving method creates better friction and will hold better.


After that wrap the rope between each of the branches vertically to cinch down on the weave and tighten the whole thing up. This is called frapping. Then finish off with another clove hitch. 


Then you can stand it up and space the branches apart. Tada! You've got a quadpod. This little structure has an endless list of uses. It can be used as the beginning of a shelter, or to hang a pot over a fire, as the starting point for a latrine or a dining table (don't get those two mixed up...). I could go on for ages.


To connect the bandana to the quadpod, I tied two half hitches around a small pebble in each corner of the bandana and tie the other end of each rope to a branch. 


I am using our Know Your Knots bandana for this one (it does feature the two knots used to create this contraption.) At this point I started filling the bandana with fine sand, then gravel and last a thick layer of dry grass. 


Next I grabbed some excessively gross water and poured it over the top of the grass. 


Here's a clip of the filter in action. You can see there's a major difference in the before and after!

The results were good. I found that I needed to run the water through a few times to get most of the sediment out, but it was certainly effective. If I were to do it again (and I probably will) I would make sure to wash the sand ahead of time. I think a lot of the first couple runs were just washing the soil from the sand out. A triple layered version of this would be more effective, but would also take more time to set up.

I would love to hear about your experiences with anything like this.