Ultralight (17g) 1-Micron Water Filter

Ultralight (17g) 1 Micron Water Filter

Water filtration systems can be bulky and heavy. Depending on the type that you choose they can also be expensive. Pumps and mechanical devices are prone to blockages or failures and chemicals alone result in a less than desirable end product. So what should you do?

I've grown more and more dissatisfied with many of the water filtration solution options on the market. The ones I've tried have worked to a degree but have been either too heavy, too needy, or too slow to be viable as truly lightweight options. So after a lot of thought and online research into materials I decided to have a go at making my own filtration system.

Gravity Water Filter

For over a year I have been using the Aquamira Frontier Pro gravity water filter system that was first written about by Jason Klass. It has been a great lightweight system for the most part, but I have had terrible issues with the flow rates of the Frontier Pro filters themselves. Some of them flowed extremely well, while others seem to hardly flow at all, more like a slow drip. Finding out that you have a brand new 'dripping' filter in the field can be a royal pain. I've even had one or two of these filters that completely refuse to flow at all. Aquamira have commented that they were aware of this issue and have improved their product design and quality controls, but I'm not willing to stick with it as my primary filter after the experiences I have had.

Some of my trail friends carry just purification tablets and swear that they have no issues with them. Technically that may be accurate, used right purification tablets can deal with most of the nasties in water, but I can't face the thought of all the crud floating around in my unfiltered water. That's one of the reasons why the SteriPen trend is definitely not for me.

After thinking about all of the different solutions I have tried over the years, some good, some not so good, I came up with the following basic requirements for my own lightweight water filtration system:

  • No moving parts to fail
  • Replaceable filter/pre-filter
  • At least 2 microns
  • Inexpensive
  • Lightweight
  • Pack small
  • Good flow rate

During my online research into water filtration options I came across a very interesting video by djbarryiii on YouTube showing how he had made a simple filter using a bio-diesel oil filtration sack bought on Ebay. It's a great video and definitely worth a look, I also have to credit this video as the original concept that sparked off my own quest for a light weight filtering solution.

My backpacking buddy Mr. Andy and I ordered a multi-pack of large bio-diesel filter bags with a 1-micron absolute rating from Ebay at a total cost of around $15. These would serve as the primary filtering material for my filtration system. For the purpose of comparison, an Aquamira Frontier Pro is rated to remove 99.9% of Cryptosporidium, Giardia and other contaminants down to 3 microns. The Aquamira Frontier Straw is rated to be 99.9% effective against waterborne pathogens and contaminants as small as 2 microns.

Filtration Material Terms:
The pore size of filter media is identified by the diameter of the particle that it can be expected to retain with a defined, high degree of efficiency. Pore sizes are usually stated in micrometer or microns for short (µm), which equals one millionth of a meter. Pore size ratings refer to the size of a specific particle or organism retained by the filter media to a specific degree of efficiency. Ratings can be stated as either nominal or absolute pore size.

An absolute pore size rating specifies the pore size at which a challenge organism of a particular size will be retained with 100% efficiency under strictly defined test conditions. Among the conditions that must be specified are: test organism (or particle size), challenge pressure, concentration and detection method used to identify the contaminant. E.g. live bacteria test. Absolute micro-filters are used for critical applications such as sterilizing and final filtration.

A nominal pore size rating describes the ability of the filter media to retain the majority of particulate at (60% - 98%) the rated pore size. Process conditions such as operating pressure, concentration of contaminant, etc., have a significant effect on the retention efficiency of the filters.

I liked the combination of pre-filter, filter, holder, and water container that Barry had shown in his video, but I had some ideas of my own on how I wanted to make a collapsable holder and make use of my existing water bladders as the containers instead of the yogurt carton shown in the video. Below is a concept sketch that I drew on the whiteboard in my office of what I was thinking.

Water Filter Concept Whiteboard

As you can see from my concept sketch, I wanted to create a cone-shaped funnel that could store flat or be rolled up with my bladders inside my backpack when not in use. I also wanted the cone holder to be quick and easy to assemble when needed. I made several paper mock-ups to make sure that the final shape fitted into the mouth opening of my Platypus and Evernew bladders and also to test out the locking tab feature that would hold the cone in place. As it turned out, getting the size was relatively easy, but tweaking the locking tab took 4-5 attempts to get just right.

Ultralight (17g) 1 Micron Water Filter

To make the cone holder I used an old disposable cutting mat that we were about to throw into the recycle bin. You can buy these cutting mats in packs of two or three at most grocery stores or big lot stores for just a few dollars - they are pretty inexpensive. This one had served its time well and was ready to move on to a loftier purpose.

Using the paper template that I had tweaked, I cut out the cone shape from the plastic cutting mat. Based on the size of the template I had created I could easily make 5-6 of these folding plastic cone holders out of the one cutting mat. I had to use a craft knife (scalpel) to make the slit where the tab of the cone slots into place. I had to lengthen the slit slightly more than m paper mockups in order for the tab to fit properly, probably just because the plastic was less flexible than paper.

Ultralight (17g) 1 Micron Water Filter

Using the larger diameter of the cone pattern as a guide, I cut out a circular piece of filter material. By pure luck I found that the plastic lid to my coffee bean container was almost perfectly the right size (6 inches in diameter) so I used that as a guide to draw my circle. As I mentioned earlier, the filter bags that we bought via Ebay were large and I estimate that I could cut out at least six filters from each bag, maybe even more if I was more careful about squeezing them together. Considering each bio-diesel filter bag cost roughly $2 a piece, that means each of my circular filters cost approximately 33c.

Ultralight (17g) 1 Micron Water Filter

With Barry's video as a guide, I folded my filter material in half and then in half again to create a quarter circle. I glued the two straight edges together on the outer edge using crazy glue and a clamp. By folding it and glueing the edges it creates a cone shape that has two pockets that can be used for filtering. Most importantly, both of the pockets do NOT have any holes at the bottom, so it guarantees that all of the water being poured into it has to pass through the 1-micron filter material.

To help preserve the longevity of the 1-micron filter material, I added a standard coffee filter to the inside of the main filter to act as a pre-filter. This will catch the majority of the crud in the dirty water and help prevent the main filter material from getting clogged up too quickly. Coffee filters are also very cheap and easy to replace. I figure I can get a few days worth of use per coffee pre-filer and carry 2-3 as part of my kit. When a pre-filter is used up I can dry it out and use it as tinder.

Ultralight (17g) 1 Micron Water Filter

The coffee filters I had (the large corrugated ones) needed to be cut down to size so that they fit nicely inside of the pocket created by the filter material. Again I used the lid of the coffee bean can as a guide for how big to cut it.

Assembling the pieces of the fitter system is very easy, there are just three parts; the plastic cone holder, the main filter material, and the coffee pre-filter. There is only one thing to be careful of which is that you are using one of the two pockets created by the folded filter material and NOT using the middle section which has a huge hole/gap in it and won't filter the dirty water properly. The combined weight of all three components is a mere 17g!

  • Coffee pre-filter: 0g
  • Main 1-micron filter: 11g
  • Plastic cone holder: 6g

My original intention was to make the plastic cone holder so that it would fit into the narrow neck of my Platypus and Evernew water bladders. After assembling the components and checking the fit I was pleased to see that it sat perfectly inside the neck of my bladders.

Testing the System
Unlike my previous gravity water filter system that could be left to hang and slowly filter the dirty water, I needed this to have a much more responsive flow rate because I would have to hold it the entire time I filtered the water. I definitely wanted to test the new system at home before taking it out on the trail.

Ultralight (17g) 1 Micron Water Filter

I started with two cups of water and poured it through the combined setup. To my surprise very little water came out through the bottom of the filter. I was bummed and thought I had messed up somewhere, not that there were an lot of steps to really screw up. Then my son Jack came to the rescue with a brilliant observation. "Dad, most of the water was soaked up by your filter." Doh, he was right. The next few cups of water that I poured through the filter had an almost perfect flow rate, slowed down just fraction by passing through the two layers of filtration material. The flow rate was amazing after getting the filters wet. My guess is that over time as both the pre-filter and main filter become clogged up, the flow rate will inevitably slow down, but for now it's excellent and I can easily swap out the coffee pre-filters.

To be safe I still plan on using Micropur water purification tablets to treat the water either before or after it has been filtered. It may or may not be necessary, but why take the chance? I've found that there is minimal bad taste from Micropur tablets, so it doesn't bother me to add them. I'd prefer not to have to wait for them to work, but time and patience is one of the benefits of being out doors and having plenty of time to relax.

I'll be testing this new filtration system a lot more in the coming weeks to make sure it is reliable and durable enough to carry with me on a trip. Unfortunately the only real way I have of testing the effectiveness is through trial and error using myself as a guinea pig. Hopefully I won't be getting sick from contaminated water in the coming weeks.

What do you think of my new water filtration system? Please leave a comment below.

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